Nellcor_N-20_Pulse_Oximeter_-_Service_manual.pdf

Service Manual

N-20/N-20P N-20/N-20P P ortabl ortable e Pul P ulss e Oximet Ox imeter er

Tyco Healthcare Group LP Nellcor Puritan Bennett Division Division 4280 Hacienda Drive Pleasanton, CA 94588 USA Toll Free 1.800.NELLCOR Authorized Representative Tyco Healthcare UK LTD 154 Fareham Road Gosport PO13 0AS, U.K.

Tyco Healthcare Group LP Nellcor Puritan Bennett Division Division 4280 Hacienda Drive Pleasanton, CA 94588 USA Toll Free 1.800.NELLCOR Authorized Representative Tyco Healthcare UK LTD 154 Fareham Road Gosport PO13 0AS, U.K.

CONTENTS

1

2

3

Introduction ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ............................ .......................... ............ 1-1 1.1

Manual Overview ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ............................ ................. ... 1-1

1.2

......................................... ............................ ............................ ............................ ............................ ............................ ..................... ....... 1-1 Warnings and Cautions ...........................

1.3

Description of N-20 Portable Pulse Oximeter Oximeter ............................ .......................................... ............................ ............................ .......................... ............ 1-1

Routine Maintenance ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ..................... ....... 2-1 2.1

......................................... ............................ ............................ ............................ ............................ ............................ ............................ ............................ ................. ... 2-1 Overview ...........................

2.2

Cleaning ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ............................ ............................ ................. ... 2-1

2.3

........................................ ............................ ............................ ............................ ........................ .......... 2-1 Periodic Safety and Functional Functional Checks ..........................

2.4

Battery........................... ......................................... ............................ ............................ ............................ ............................ ............................ ............................ ........................... ..................... ........ 2-1

Performance Verification ........................... ......................................... ............................ ............................ ............................ ............................ .......................... ............ 3-1 3.1

Introduction ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ............................ .......................... ............ 3-1 Required Materials

CONTENTS

8

9

7.1

General Instructions ........................... .......................................... ............................. ............................ ............................ ............................. ............................. ........................ .......... 7-1

7.2

.......................................... ............................ ............................ ............................ ............................ ........................ .......... 7-1 Repacking in Original Carton............................

Specifications ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ............................ ........................ .......... 8-1 8.1

......................................... ............................ ............................ ............................ ............................ ............................ ............................ ............................ ................... ..... 8-1 Readout ...........................

8.2

Controls ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ............................ ............................ ................. ... 8-1

8.3

Operating Modes............................ .......................................... ............................ ............................ ............................ ............................ ............................ ............................ ................. ... 8-1

8.4

.......................................... ............................ ............................ ............................ ............................ ............................ ............................ ..................... ....... 8-2 Printer Output ............................

8.5

N-20/N-20P Performance............................ .......................................... ............................ ............................ ............................ ............................ ............................ ................. ... 8-2

8.6

.......................................... ............................ ............................ ............................ ............................ ............................ ............................ ........................ .......... 8-3 Sensor Types ............................

8.7

Electrical Specifications Specifications ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ................... ..... 8-3

8.8

.......................................... ............................ ............................ ............................ ............................ ........................ .......... 8-3 Environmental Specifications Specifications ............................

8.9

Physical Specifications Specifications ............................ .......................................... ............................ ............................ ............................ ............................ ............................ ..................... ....... 8-4

Technical Supplement ........................... ......................................... ............................ ............................ ............................ ............................ ............................ ................... ..... 9-1 9.1

......................................... ............................ ............................ ............................ ............................ ............................ ............................ ............................ ................. ... 9-1 Overview ...........................

9.2

Functional versus Fractional Saturation Saturation ........................... ......................................... ............................ ............................ ........................... ..................... ........ 9-1

CONTENTS Figure 9-7: Printer Control Block Diagram....................................................................................................... 9-5 Figure 9-11: Variable Gain Circuit.................................................................................................................... 9-9 Figure 9-12: Filtering Circuit............................................................................................................................ 9-10 Figure 9-4: Digital Circuitry Block Diagram.................................................................................................... 9-12 Figure 9-14: N-20 Hardware Block Diagram................................................................................................... 9-14 Figure 9-15: Address Demultiplexing Circuit .................................................................................................. 9-15 Figure 9-16: Address Decoding Circuit............................................................................................................ 9-16 Figure 9-17: CPU Memory Circuit ................................................................................................................... 9-17 Figure 9-18: Input Port Circuit......................................................................................................................... 9-18 Figure 9-20: Real-Time Clock Circuit .............................................................................................................. 9-19 Figure 9-21: Audio Output Circuit ................................................................................................................... 9-20 Figure 9-6: Display Control Block Diagram.................................................................................................... 9-20 Figure 9-23: User Controls Circuit................................................................................................................... 9-22 Figure 9-26: Analog Reference Voltage Circuit............................................................................................... 9-25 Figure 9-27: Ambient Light Circuit.................................................................................................................. 9-25 Figure 9-28: Ambient Temperature Circuit..................................................................................................... 9-26 Figure 9-29: Battery Voltage Circuit ................................................................................................................ 9-26 Figure 9-30: Battery Type Circuit .................................................................................................................... 9-26 Figure 9-32: Printer Flex Circuit ...................................................................................................................... 9-28 Figure 9-8: LED Drive Circuit ......................................................................................................................... 9-31 Figure 9-9: Differential Synchronous Demodulation Circuit........................................................................ 9-33 Figure 9-10 N-20 HSO Timing Diagram ......................................................................................................... 9-35 Figure 9-13: AC Variable Gain Control Circuits............................................................................................ 9-37 Figure 9-19: Output Port Circuit...................................................................................................................... 9-39 Figure 9-22: Display Control Circuit................................................................................................................ 9-41 Figure 9-24: Power Supply Circuit................................................................................................................... 9-43 Figure 9-25: Power Control Circuit.......... 9-45

1

INTRODUCTION

1.1 Manual Overview 1.2 Warnings and Cautions 1.3 Description of the N-20 Portable Pulse Oximeter

1.1

Manual Overview This manual contains service information for the Nellcor ® portable pulse oximeter, models N-20/N-20P, that is necessary to maintain and repair the N-20/N-20P by qualified service personnel. Note that models designated for sale in Europe differ from models designated for sale in the USA only in that the user control buttons and display use icons rather than alphabetical characters, and that the product labels reflect the appropriate European certifications and company addresses.

1.2

Warnings and Cautions "WARNING" is used to call attention to procedures that could result in an error in calibration or performance, and/or precautions that are important to ensure the safety of both service personnel and patients. "CAUTION" is used to call attention to procedures that should be carefully followed to prevent damage to the instrument.

1.3

Description of N-20 Portable Pulse Oximeter

2

R OUTI OU TIN N E MA I N TE N A NC E

2.1 Overview 2.2 Cleaning 2.3 Periodic Safety and Functional Checks

2.4 Battery

2.1

Overview The N-20/N-20P requires no routine maintenance, routine service, or calibration. If service is necessary, contact qualified service personnel or Nellcor’s representative. Use only Nellcor-approved test equipment when running a performance test on the N-20/N-20P. The user's institution and/or local or national agencies may require testing.

2.2

Cleaning Dampen a cloth with a commercial, commercial, nonabrasive cleaner, and lightly wipe the surfaces of the N-20/N-20P. Do not spray or pour liquid on the instrument instrument or accessories. Do not allow liquid to contact connectors, switches, or openings in the chassis.

2.3

Periodic Safety and Functional Checks The following checks should be performed at least every 2 years by a qualified service technician.

3

P E R F OR MA NC E V E R I F IC A TION TI ON

3.1 Introduction 3.2 Required Materials 3.3 Performance Tests

Caution: Adhere Adhere to all testing instructions; failure failure to do so may damage the N-20/N-20P.

3.1

Introduction This section describes performance verification for the N-20 and N-20P pulse oximeters (hereafter called the “monitor”), following repairs. The N-20/N-20P are powered by alkaline batteries. The N-20/N-20P design includes built-in electrical electrical insulation; no ground resistance resistance or electromagnetic electromagnetic leakage testing is required. The tests can be performed without removing the monitor cover. If the monitor fails to perform as specified in any test, repairs must correct the discrepancy before the monitor is returned to the user.

3.2

3.3

Required Materials Durasensor

Nellcor DS-100A

Tester, Pulse Oximeter

Nellcor SRC-2

Performance Tests

Performance Verifi cation

N-20 (no printer)

37 hours with Alkaline batteries.

N-20/P (with printer)

32 hours with Alkaline batteries.

This test requires a new set of batteries. The new batteries must be installed after the test. Connect the Nellcor SRC-2 pulse oximeter tester to the monitor. Set the switches on the SRC-2 as follows: Switch Setting RATE

38

LIGHT

LOW

MODULATION

LOW

RCAL/MODE RCAL 63/LOCAL Momentarily press the MEASURE button, and verify the following power-up sequence: All indicators—OXYGEN SATURATION, PULSE RATE, PULSE SEARCH, LOW BATTERY, and the PULSE BARS—light for a few seconds. Verify the OXYGEN SATURATION, and PULSE RATE displays indicate "888.” The OXYGEN SATURATION display momentarily indicates the monitor 3-digit software version. The other displays are not lit. Software versions may vary depending on the type of monitor and the date of manufacture. The N-20P will display printer status immediately after displaying the software version. The OXYGEN SATURATION display will indicate “Pr”and the PULSE RATE display will indicate either “On” or “OFF.” The OXYGEN SATURATION display momentarily indicates the letters ”tSt” and the monitor sounds


During the next few seconds, the instrument: • • •

Switches off the display backlight; Displays three digits in the Oxygen Saturation display field representing the software version (for example, 123 is software version 1.2.3). Only the N-20P displays the printer status in the display fields; that is, either "Pr On" or "Pr OFF."

If a sensor is attached to the instrument, a zero ("0") appears in first position of the display fields. The Pulse Search indicator flashes; if no sensor is attached to the instrument, horizontal dashes appear in all six Oxygen Saturation and Pulse Rate display fields, and the Pulse Search indicator flashes. After approximately 1 minute, a short beep occurs and the instrument automatically switches off. If at any time during the test sequence "Err" followed by a code number is displayed, make a note of the error code and refer to Section 4.7, Error Codes, for a description. 3.3.3.1 How To Run the Self-Test

Place a new set of batteries in the monitor. Do not connect a sensor or SRC-2 to the monitor. Momentarily press the MEASURE button, verify the following power-up sequence: All indicators—OXYGEN SATURATION, PULSE RATE, PULSE SEARCH, LOW BATTERY, and the PULSE BARS—light for a few seconds. Verify that the OXYGEN SATURATION and PULSE RATE displays indicate "888."


ADV D/D combinations 1. 2.

3.

Ad dd Err

Press the Measure button: "9O" appears in the Oxygen Saturation display. Press the Battery-Check button: "bAt" appears in the Oxygen Saturation display.

Press the printer ON button: "On" appears in the Oxygen Saturation display. A printer test pattern prints out; the following is an approximate example of the test pattern:

Examine the test pattern to verify that all dots print with a uniform darkness. Overall printout darkness can be adjusted; to adjust printer darkness, see paragraph 4.6.7. If printout darkness is


4.

5. 6.

All indicators—OXYGEN SATURATION, PULSE RATE, PULSE SEARCH, LOW BATTERY, and the PULSE BARS—light for a few seconds. Verify that the OXYGEN SATURATION and PULSE RATE displays indicate "888.” The OXYGEN SATURATION display momentarily indicates the monitor 3 digit software version. The other displays are not lit. Software versions may vary depending on the type of monitor and the date of manufacture.

The N-20P will display printer s tatus immediately after software version display. The OXYGEN SATURATION display will indicate “Pr,” and the PULSE RATE display will indicate either “On” or “OFF.” The OXYGEN SATURATION display momentarily indicates the letters ”tSt” and the monitor sounds a single tone. The other displays are not lit. “tSt” verifies that the monitor recognizes that a tester is connected. The OXYGEN SATURATION and PULSE RATE displays indicate “0,” the PULSE SEARCH indicator is flashing, and the PULSE BAR will start to register the simulated pulse. After a few beats a pulse tone will be heard, and the PULSE SEARCH indicator will turn off. The OXYGEN SATURATION display indicates between 79 and 83 and the PULSE RATE display indicates between 37 and 39.

3.3.6.2 Normal Operation

These tests are an overall qualitative check of the system and require connecting a live subject to the monitor:


TEST RESULTS

Model:

N-20

Serial:_____________________________

Date:___________Customer Name:________________________________

Description

Pass

Fail

Performance Tests

_____

____

Backlight Test

_____

____

Battery Performance

_____

____

Testing the Low Battery Indicator

_____

____

Power-Up Performance

_____

____

How to Run the Self-Test

_____

____

Printer Test

4

TROUBLESHOOTING

4.1 How to Use This Section 4.2 Who Should Perform Repairs 4.3 Replacement Level Supported 4.4 Obtaining Replacement Parts 4.5 Troubleshooting Guide 4.6 Service Procedures 4.7 Error Codes

WARNING: Disassembly of the instrument exposes hazardous voltages. To avoid injury or instrument damage, disassembly or maintenance must be attempted only by qualified service personnel.

4.1

How to Use this Section This section explains how to identify and correct monitor difficulties and provides procedures for common service-related activities, such as battery replacement, clearing paper jams, and adjusting printer darkness. Use this section in conjunction with Section 3, Performance Verification, and Section 6, Spare Parts.

Troubleshooting

4.5

Troubleshooting Guide This section discusses potential symptoms, possible causes, and actions for their resolution. Should this troubleshooting guide fail to address the symptoms evident in a particular N-20/N-20P, please contact Nellcor's Technical Services Department or a local Nellcor representative for assistance. If the N-20/N-20P does not perform as expected: • • •

Check for proper sensor placement. Depending on concentration, indocyanine green, methylene blue, and other intravascular dyes may affect the accuracy of a measurement. These instruments are calibrated to read oxygen saturation of functional arterial hemoglobin (saturation of hemoglobin functionally capable of transporting oxygen in the arteries), and significant levels of dysfunctional hemoglobins such as carboxyhemoglobin or methemoglobin may affect the accuracy of a measurement.

If the electronics and/or display functions require testing, refer to Section 3, Performance Verification.

Symptom 1: No response to Measure button. Cause

Action

Battery access door may not be properly latched.

Check access door and ensure it is properly latched.

Batteries may be discharged.

Exchange them for a new set.

Batteries may be incorrectly installed.

Ensure that batteries are oriented according

Troubleshooting

Symptom 2: Pulse Search indicator appears for more than 5-10 seconds. Cause

Action

Sensor may be improperly positioned.

Ensure the sensor is correctly applied (see sensor directions for use).

Incorrect sensor may be in use.

See sensor directions for use to ensure that the patient's weight and sensor application is correct. Test the sensor on another person to verify proper operation.

Perfusion may be too low.

Check patient status. Test the instrument on someone else, or try another type of sensor. The N-20/N-20P will not make a measurement if perfusion is inadequate.

Foreign material on the sensor LEDs or photodetector may be affecting performance.

Clean the test area and ensure that nothing blocks the sensor site.

Patient motion may be interfering with the instrument's ability to find a pulse pattern.

If possible, ask the patient to remain still. Verify that the sensor is securely applied and replace it if necessary, move it to a new site, or use a sensor that tolerates patient movement, such as an appropriate adhesive sensor.

Environmental motion may be interfering with the instrument's ability to track a pulse The sensor may be too tight, there may be excessive illumination (e.g., a surgical or bilirubin lamp or direct sunlight), or the sensor may be placed on an extremity with a blood pressure cuff, arterial catheter, or intravascular line.

Troubleshooting

Cause The printer is not operational, but the N-20P continues to obtain patient measurements.

Symptom 6:

Action Check to see if the paper is jammed. Examine the print head and ensure that it has returned to the home position.

Err followed by a number appears on the display. Cause

See Section 4.7 for error codes.

Symptom 7:

Action Record the number that is displayed.

Time or date is incorrect (N-20P only). Cause

The real-time clock (RTC) battery may be exhausted.

Action Replace the RTC battery (see Section 4.6.4). Reset the time and date (see Section 4.6.3).

Symptom 8:

Printer fails to operate (N-20P only). Cause

Fuse F2 on the auxiliary PCB may be open.

Action See paragraph 4.6.5 for information about fuses.

Troubleshooting

4.6.1

Installing Batteries

1. 2. 3. 4.6.2

Remove the battery cover access door by pressing the battery compartment access door latch.

Install four alkaline "C" cell batteries. Be sure to observe the polarity indicator sticker. Replace the battery cover access door.

Loading/Clearing Printer Paper

The N-20P uses a thermal paper that can show printed characters on one side only. Make sure that the paper roll is correctly installed; always refer to the graphical instruction label found on the paper roll. 1. 2. 3. 4.

Press down and outward on the top of the paper compartment door to remove it. Feed the paper into the paper compartment slot; refer to the graphic label for orientation. Press and hold the ADV button until the end of the paper appears at the paper exit slot. Replace the paper compartment door.

If the paper jams either during the loading process or during printing, proceed as follows: 1. 2.

3.

4.

Remove both the paper door and the printer-head access cover. Firmly grab and pull the paper roll backward—out and away from the print head—observe the access to the print head to determine whether or not the paper escaped from the jammed position. If paper remains jammed between the print head and printer, press the ADV button; the jammed paper may work its way out. If the paper remains jammed, and the printer drive does not advance the paper, manually advance the drive gear on the side of the printer to free the paper. If these attempts fail to free the jammed paper, remove the printer from the unit to gain full access (see paragraph 5.3, N-20 Disassembly Procedure).

Troubleshooting

13.

4.6.4

Date and time are now correct. Check by switching on the N-20P with the printer enabled. After the N-20P executes its Power-On Self-Test, the printer prints the spot check mode header with the correct date and time.

Replacing the Real-Time Clock (RTC) Battery

The socket for the RTC battery (BT1) is located on the auxiliary PCB at grid location 5D. Typical life of the clock battery is 5 years. 1. 2. 3. 4. 5. 4.6.5

Disassemble the N-20 (see Section 5.3, N-20, Disassembly Procedure). Using a thin flathead screwdriver, gently pry the RTC battery from its socket. Insert a new battery into the socket, observing the polarity indication (socket's clip and battery's flat side are positive). Reassemble the unit. Reset the clock (see paragraph 4.6.3, Setting Date and Time).

Replacing Fuses

Two fuses (F1 and F2) are located on the auxiliary PCB. Fuse F1 may open to protect the CPU and its associated components from damage if the power supply malfunctions. Fuse F2 may open to protect the printer from damage due to excessive voltage if the printer head jams or has been physically damaged. Refer to the auxiliary PCB schematic for the locations of F1 and F2. 4.6.6

Replacing the DB-9 Connector

1. 2.

Disassemble the N-20 (see Section 5.2); the connector is on the main PCB at grid location 3A. Using a low-power soldering iron, unsolder the connector from the PCB and remove it. Save all Teflon tubing, ferrite blocks, and insulating materials for the replacement connector.

Troubleshooting

Note: The parenthetic line description is not printed, and button presses are ignored whenever the printer is printing. 1.

Press the ADV button to change the darkness setting. The printer prints a line with each button press, and the setting increments from lighter to darkest and then wraps back to lighter. 2. Allow the N-20P to switch off (about 30 seconds). The last print darkness setting is remembered when the N-20P is switched back on. Test this by repeating the procedure and skipping step 3.

4.7

Error Codes If a failure is detected during the Power-On Self-Test or during any performance test, the error message (Err) appears in the Oxygen Saturation display and a 3-digit error code number appears in the Pulse Rate display. If an error message appears, find its category (the first digit of the error code represents the category) and record the error code number. Match the number to the description in the following table, and contact Nellcor's Technical Services Department or Nellcor's local representative for assistance. Internal tests are performed in the order of the table listing. The first error condition encountered is the one displayed.

4.7.1

Category 1 — Microprocessor Errors

Table 4-1: Microprocessor Error Codes Errors in the CPU (main PCB). Likely action is replacement of the CPU. 101

Error in internal RAM registers test

102

Error in zero register test

Troubleshooting

4.7.3

Category 3 — PROM Errors

Errors in PROM memory (main PCB). Likely action is replacement of the PROM. 301 4.7.4

Error in PROM test

Category 4 — I/O Port Errors

Errors in the CPU's internal I/O port (main PCB). Likely action is replacement of either the CPU or the main PCB. 401–409

Errors in I/O port test

4.7.5

Category 5 — Reserved

4.7.6

Category 6 — Clock Errors

Failure of the real-time clock (auxiliary PCB), or timing differences between the CPU’s clock and the real-time clock. Likely action is replacement of the main or auxiliary PCB.

4.7.7

601

Failure of real-time clock

602, 603

Errors in real-time clock

Category 7 — Watchdog-Timer Errors

Error in the watchdog-timer circuit of the CPU (main PCB). Likely action is replacement of the CPU. 701, 702

Errors in watchdog-time

5

DIS A S S E MB LY G UIDE

5.1 Introduction 5.2 Required Equipment/Tools 5.3 N-20 Disassembly Procedure 5.4 N-20P Disassembly Procedure

WARNING: Only qualified service personnel must perform repair and testing. Improper repair and/or adjustment may compromise patient safety or the accuracy of the instrument.

5.1

Introduction The N-20/N-20P can be disassembled down to all major component parts, including: • • • •

PCBs battery cables chassis enclosures

WARNING: Before attempting to open or disassemble the N-20/N-20P, disconnect the power cord. Caution: Observe ESD (electrostatic discharge) precautions when working within the unit.

Dis as s embly G uide

20

21

34

19

Figure 5-1: Sensor Lock, and Printer, Paper, and Battery Access Doors 1. 2. 3.

Remove the battery door (19) and batteries. Remove the sensor lock (34) by lightly pressing in on its ears and pulling out from the sensor shroud. Remove the paper door (20) and paper roll, and the printer door (21).


5.2.2

Removing the Covers

16

18

27 26


5.2.3

Removing the PCBs and Display Assembly

Tab #1

Tab #3

18 Detail B

Flex #1

6

Tab #4 Tab #2 Flex #3

Flex #2 Detail A 5

27 11 12 13 26

Figure 5-3: Main, Auxiliary, and Display PCB Assembly 1. 2.

Remove the Measure button (6) from the main PCB. Remove the entire PCB/Taliq display assembly from the rear cover by tilting opposite the


5.2.5

Disassembling the Printer/Flex Circuit Assembly 29 32

4

7

37

28

6

SPARE PARTS

6.1 N-20/N-20P Spare Parts

6.1

N-20/N-20P Spare Parts To order replacement parts, contact Nellcor's Technical Services Department and order by part number. Item numbers correspond to the callout numbers in the figures. Item

Designator

Description

P/N

1

SW1

Battery switch (auxiliary PCB)

630106

2

BT1

Battery holder (auxiliary PCB)

901582

3

BT1

Battery, lithium (auxiliary PCB)

640112

4

Bracket, printer, hold-down

023133

5

Button, battery-check

023301

Button, measure

022948

Button, measure (European version)

026386

Buttons, printer, strip

022947

Buttons, printer, strip (European version)

026387

Connector shield, DB-9

023467

Connector, DB-9

463103

6

S2

7 9 10

P1

S pare Parts

Item

Designator

Description

P/N

31

Screw, captive

891324

32

Screw, Phillips, 4-40 ×1/4

801025

33

Screw, plastite

871031

34

Sensor lock

022943

35

Sensor shroud

022944

36

Spacer

023452

37

Stiffener, printer button

023131

38

Tape, foam (.88" ×.38")

023300

Transducer, audio, piezo ceramic

691230

39

BZ1

7

PAC K ING FOR SHIPME NT

7.1 General Instructions 7.2 Repacking in Original Carton 7.3 Repacking in a Different Carton

Should you need to ship the N-20/N-20P monitor for any reason, follow the instructions in this section.

7.1

General Instructions Pack the monitor or printer carefully. Failure to follow the instructions in this section may result in loss or damage not covered by the Nellcor warranty. If the original shipping carton is not available, use another suitable carton or call Nellcor Technical Services to obtain a shipping carton. Prior to shipping the device, contact Nellcor Technical Services for a returned goods authorization (RGA) number. Mark the shipping carton and any shipping forms with the RGA number.

7.2

Repacking in Original Carton If available, use the original carton and packing materials. Pack the monitor or printer as follows: Place the monitor, or printer, and, if necessary, accessory items in original packaging. Place in shipping carton and seal carton with packing tape. Label carton with shipping address, return address, and RGA number.

8

SPECIFICATIONS

8.1 Readout 8.2 Controls 8.3 Operating Modes 8.4 Printer Output 8.5 N-20/N-20P Performance 8.6 Sensor Types 8.7 Electrical Specifications 8.8 Environmental Specifications 8.9 Physical Specifications 8.10 Quality Information

8.1

Readout Display shows SpO2 (saturation of arterial hemoglobin oxygen), pulse rate, and pulse amplitude; also included are a Pulse Search and Low Battery indicator, and an electroluminescent backlight.

8.2

Controls

8.2.1

N-20

The Measure button switches the instrument on and off, and initiates the measurement cycle.

S peci fications

For the N-20, a 2% or greater decrease in SpO2 is indicated by two brief, low-pitched tones. The N-20P printout shows SpO2 and pulse rate at 30-second intervals. For the N-20P, a 2% or greater decrease in SpO2 is indicated by two brief, low-pitched tones and an asterisk (*) on the printout. At the end of the measurement period, a header and statistical summary values (minimum, maximum, and mean of both pulse rate and oxygen saturation) are printed.

8.4

Printer Output When activated by the printer ON button, the N-20P output shows date, time, SpO2, and pulse rate (in spot check mode), with space provided for writing in patient identification. The thermal paper printout measures roughly 40 mm (1.6 in.) by 100 mm (4.0 in.) in size. If the N-20P is in spot check mode and the printer is turned on any time during a measurement or after a measurement is taken and before the N-20P powers down, the printer will catch up and print a complete record of the measurements recorded up to the current moment.

8.5

N-20/N-20P Performance

8.5.1

Range

8.5.2

Saturation:

0–100%

Pulse Rate:

20–250 beats per minute (bpm) ± 1 standard deviation

SpO2 Accuracy

1

S peci fications

8.6

Sensor Types Table 8-1: Sensors Sensor

Model

Patient Size

Oxisensor II oxygen transducers (sterile, single-use only)

N-25/N-25LF I-20/I-20LF D-20 D-25/D-25L R-15

<3 or >40 kg 3 to 20 kg 10 to 50 kg >30 kg >50 kg

Oxiband oxygen transducer (reusable with disposable nonsterile adhesive)

OXI-A/N OXI-P/I

<3 or >40 kg 3 to 40 kg

Durasensor oxygen transducer (reusable, nonsterile)

DS-100A

>40 kg

Nellcor reflectance oxygen transducer (reusable, nonsterile)

RS-10

>40 kg

Dura-Y multisite oxygen transducer (reusable, nonsterile)

D-YS

>1 kg

D-YSE

>30 kg

D-YSPD

3 to 40 kg

For use with the Dura-Y sensor: Ear clip (Reusable, nonsterile) Pedi-Check ™ pediatric spot-check clip (reusable, nonsterile)

S peci fications

8.8.2

Storage Temperature

-20 to 50 °C (4 to 122 °F)

8.9

Humidity:

Any humidity/temperature combination without condensation

Altitude:

0 to 6200 meters (0 to 20,000 ft)

Physical Specifications Physical specifications are based on product without the protective boot.

8.9.1

8.9.2

Weight (with batteries installed)

N-20:

0.6 kg (1.3 lb)

N-20P:

0.62 kg (1.4 lb)

Dimensions

N-20:

19.0 cm high ×7.6 cm wide ×5.08 cm deep (7.5 in. ×3.0 in. ×2.0 in.)

N-20P:

19.0 cm high ×7.6 cm wide ×6.35 cm deep (7.5 in. ×3.0 in. ×2.5 in.)

8.10 Qualifying Information

9

TECHNICAL SUPPLE ME NT

9.1 Overview 9.2 Functional versus Fractional Saturation 9.3 Measured versus Calculated Saturation 9.4 Circuit Analysis 9.5 Functional Overview 9.6 Definition of Terms 9.7 Overall Block Diagram 9.8 SpO2 Analog Circuit 9.9 Digital Circuitry 9.10 Circuit Illustrations

9.1

Overview The N-20/N-20P is based on the principles of spectrophotometry and optical plethysmography. Optical plethysmography uses light absorption technology to reproduce wave forms produced by pulsatile blood. The changes that occur in the absorption of light due to vascular bed changes are reproduced by the pulse oximeter as plethysmographic wave form. Spectrophotometry uses various wavelengths of light to qualitatively measure light absorption through given substances. Many times each second, the N-20/N-20P passes red and infrared light into

Techni cal Supplement

Figure 9-1 illustrates the effect that variations in pH, temperature, partial pressure of carbon dioxide (PCO2), and concentrations of 2,3-DPG and fetal hemoglobin may have on the oxyhemoglobin dissociation curve.

Figure 9-1: Oxyhemoglobin Dissociation Curve

Techni cal S upplement

Main PCB

Patient sensor

SpO2 analog Microprocessor Memory Display control Sensors: temperature ambient light battery voltage

PROM

Measure button

20-pin headers

Auxiliary PCB Power supply Printer interface Display control Audio beeper

Batteries

4-6 VDC

Realtime clock

Flex connectors

Check battery button

Display backlight

Printer flex circuit

Printer

N-20P only

Figure 9-2: Overall Block Diagram 9.6

SpO2 Analog Circuitry Block Diagram (Figure 9-3) Analog circuitry has high signal sensitivity and reduced susceptibility to noise. Its design allows for a


9.6.1

Digital Circuitry Block Diagram (Figure 9-4)

Figure 9-4 shows the N-20/N-20P hardware and circuits, which include the CPU and system memory, the power supply and power control circuitry, user controls, display and ambient light sensors, audio output, thermal printer (N-20P only) and ambient temperature sensor, and the real-time clock.

Measure Check Battery

Power supply & control

N-20/N-20P Control buttons

AUX PCB

Ambient light sensor

Main PCB AUX PCB

CPU

Display drivers

Main PCB Memory & software

Display

Audio beeper

AUX PCB (N-20 only)

Printer

To analog section Real-time clock

AUX PCB

Ambient temp. sensor

Main PCB

ON

ADV

D/D

Printer Control button


9.6.3

Display Control Block Diagram (Figure 9-6)

The N-20/N-20P display is controlled by the display control circuitry (see Figure 9-6). A sensor is used to measure ambient light. During low light conditions, the display backlight, an electroluminescent device, is automatically switched on. Main PCB

Microprocessor

Main PCB

AUX PCB

Control conditioning circuit (generates timing signals)

Display driver (1) Display Display driver (2)

Display backlight

AUX PCB High voltage control circuit (enables +70 VDC to display)

70 volts

Figure 9-6: Display Control Block Diagram 9.6.4

Printer Control Block Diagram (Figure 9-7)

Printer circuitry (Figure 9-7) is divided into two subsections: the printer interface and the printer flex circuit. The printer interface circuitry is present on all models, but is disabled by software in the N-20. The printer flex circuit is added when a printer is present.


9.7.4

High Speed Outputs (HSO)

The 6 HSO lines control most of the timing of the LED signal pulse and the demodulation of the received signal. 9.7.5

Input and Output (I/O)

Input and Output (I/O) are digital lines that are used by the CPU to read in data and output data. 9.7.6

Light-Emitting Diodes (LEDs)

Two LEDs are used in Nellcor oximetry sensors. Light is transmitted through body tissue and received by a photodetector circuit that converts it to photocurrent. The two wavelengths, which are used for calculation of pulse rate and oxygen saturation in blood, are transmitted at the following frequencies: • •

9.7.7

infrared (IR) light at approximately 915 microns red light at approximately 660 microns

Pulse Width Modulation (PWM)

The three 8-bit PWM outputs can be software controlled; their duty cycle can be changed from 0-255/256 of the total pulse duration. PWM frequency is the crystal frequency of the CPU, which is 10 MHz divided by 1024. The PWMs control the gains within the analog circuit. 9.7.8

RCal

Sensor RCal value is a resistance value specific to an individual sensor. This value is used by the


9.9

SpO2 Analog Circuitry This subsection describes the SpO 2 analog hardware. The analog circuitry has high signal sensitivity and reduced susceptibility to noise. Its design allows for a wide range of input signal levels and a broad range of pulsatile modulation. The SpO2 analog block diagram (Figure 9-3) consists of four subsections:

9.9.1

Sensor Output/LED Control

The CPU controls the gain of both LEDs so that signals received at the input amplifier are within an acceptable dynamic range. Signal channel gain may also need to be increased. The CPU uses PWM lines to control LED current level or to amplify the signal channel. 9.9.2

Input Conditioning

Sensor output current is converted to voltage. A demodulation circuit minimizes the effects of other light sources and stray frequency inputs. Because the IR and RED signals are at different current levels, the two LED signals are demultiplexed and separately amplified, so they can be compared with each other. Two circuits handle the demultiplexing by alternately selecting LED signals using switches. Filters then remove noise and smooth the signals before sending them to the amplifiers. 9.9.3

Signal Gain

The separated LED signals are amplified so that their current levels are within the A/D converter's acceptable range. The signals are filtered to improve the signal-to-noise ratio, and clamped to a


9.9.5.1 LED Drive Circuit

The LED drive circuit is illustrated in Figure 9-8 (at the end of this section). The IR and red LEDs are separately controlled with their drives’ currents multiplexed over two shared wires. Current to the IR LED is in the range of 4.3-50.0 mA; and, current to the red LED is in the range of 6.5-75.0 mA. Currents are limited to less than 100 mA for two reasons: (1) slight excess current can potentially change the emission characteristics of the LEDs, and (2) large excess current could create excessive heat at the sensor site. The IR/red LED transmission signal (HSO1 of the CPU) is fed into the select inputs of the triple single-pole-double-throw (SPDT) analog multiplexing switch U10, causing either the IR or the red LED transmission to be enabled.

PWM1, which is filtered by the network of R44, C37, R52, and C38, is input to the LED drive circuit switch U10, and controls the magnitude of the IR LED current supply. PWM2, which is filtered by the network of R43, C36, R53, and C39, is also input to U10, and controls the red LED current magnitude. Two NPN transistors (Q1 and Q2) act as current sources for the IR and red LED outputs. Two PNP transistors (Q3 and Q4) act as switches between the IR and red LED output lines. Transistor Q5 acts as an LED drive current limiter; it clamps output of the current regulator circuit to the required level. If any resistor in the LED drive circuit fails, current to the LED will still be limited to a safe level. The RSENS line senses the RCal value and enables the CPU to make the proper calculations based on the type of sensor being used.


coordinated with the LED transmission so that the IR and red signals are each sampled twice per cycle; that is, once when the LED is off (signal inverted), and once when the LED is on (signal not inverted). The filtering circuit that follows has a long time constant, thereby acting as an averaging circuit. A simplified N-20 HSO timing diagram is illustrated in Figure 9-10 (at the end of this section). If the instantaneous average photocurrent (DC offset) is excessive and U1D cannot bring it to VREF, the PHOTOI line to the CPU (HSI0) is activated. This action is an indication of excess ambient light into the photosensor, or the occurrence of excess noise in the input circuit. It also serves as a warning to the instrument that the sensor signal may be contaminated and causes the software to send an error message. After about 3 seconds of continuous photocurrent signal, pulse search annunciation will begin. After about 10 seconds of continuous photocurrent signal, zeros will be displayed. 9.9.7

Signal Gain

The separated IR and red signals are amplified so that their DC values are within the range of the A/D converter. Because the received IR and red signals are typically at different current levels, the signal gain circuits provide independent amplification for each signal as needed. The gain in these circuits is adjusted by means of the PWM lines. After the IR and red signals are amplified, they are filtered to improve the signal-to-noise ratio and clamped to a reference voltage to prevent the combined AC and DC signal from exceeding an acceptable input voltage from the A/D converter. 9.9.7.1 Variable Gain Circuits


The two variable gain circuits are functionally equivalent. The gain of each circuit is contingent upon the signals received level and is controlled to bring each signal to approximately 3.5 V. Each circuit uses an amplifier and one switch in the triple SPDT analog multiplexing unit U2. The gain in each of the circuits is accomplished by means of a feedback loop, which includes one of the SPDT switches in U2. The PWMs control whether the feedback loop is connected to ground or to the amplifier output. The feedback is then averaged by C33/R25 (red), and C34/R24 (IR). The higher the value of PWM2, the greater the IR gain; the higher the value of PWM1, the greater the red gain. 9.9.7.2 Filtering Circuits

The filtering circuits are illustrated in Figure 9-12. These circuits consist of two cascaded second-order filters with a break frequency of 10 Hz. Pairs of diodes (D1/D3 and D2/D4), that are located between VREF and ground at the positive inputs of the second amplifiers, maintain the voltage output within the range of the A/D converter. C13 REDDC

TP81 .12UF RED

R6 100K

C16

.12UF

11 15

R7 100K

U4D 16

14 OP490SO

R9 100K C14

C15 .068UF

R8

10 12

100K TP89

U4C

CR1

OP490SO VREF


otherwise be required to accurately compare the IR and red modulations between the combined AC and DC signals. The DC offsets are subtracted by using an analog switch to set the mean signal value to the mean of the range of the A/D converter whenever necessary. The AC modulation is then superimposed upon that DC level. This is also known as AC ranging. Each AC signal is subsequently amplified such that its peak-to-peak values span one-fifth of the range of the A/D converter. The amplified AC signals are then filtered to remove the residual effects of the PWM modulations and, finally, are input to the CPU. The combined AC and DC signals for both IR and red signals are separately input to the A/D converter. 9.9.8.1 Offset Subtraction Circuits

The AC variable gain control circuit is illustrated in Figure 9-13 (at the end of this section). Voltage dividers R22 and R41 (red), and R31 and R5 (IR), which are located between VREF and ground, establish a baseline voltage of 2.75 V at the input of the unity gain amplifiers U7C (red) and U7D (IR). Whenever SPST analog switches U11A and U11D are closed by HSO0 (active low), the DC portions of the IR and red signals create a charge, which is stored on C29 and C89, respectively. These capacitors hold this charge even after the switches are opened and the resulting voltage is subtracted from the combined signal— leaving only the AC modulation output. This AC signal is superimposed on the baseline voltage output by U7C and U7D. The IRDC and REDDC are then filtered and input to the CPU, and can be measured at TP58 and TP54, respectively. 9.9.8.2 AC Variable Gain Control Circuits

The AC variable gain control circuit is illustrated in Figure 9-13 (at the end of this section).


Measure Check Battery

Power supply & control

N-20/N-20P Control buttons

AUX PCB

Ambient light sensor

Main PCB AUX PCB

CPU

Display drivers

Main PCB Memory & software

Display

Audio beeper

AUX PCB (N-20 only)

Printer

To analog section Real-time clock

AUX PCB

Ambient temp. sensor

Main PCB

ON

ADV

D/D

Printer Control button

Figure 9-4: Digital Circuitry Block Diagram

9.10.1

CPU

A 16-bit microcontroller that includes a serial port, watchdog timer, A/D converter with an 8-input analog multiplexer, 3-pulse width modulators, and a high-speed I/O subsystem.


9.10.8

Thermal Printer (N-20P only)

Generates a hard copy of oxygen saturation and pulse rate values. A sensor monitors ambient temperature and adjusts printer output to ensure consistent print quality. 9.10.9

CPU

The CPU circuit is illustrated in Figure 9-14. The Intel 80C196KC CPU is a 16-bit microcontroller with built-in peripherals including: a serial port, watchdog timer, A/D converter with an 8-input analog multiplexer, three pulse width modulators, two 16-bit counter/timers, up to 48 I/O lines, and a high-speed I/O subsystem. The CPU is capable of running up to 16 MHz, but it is run at 10 MHz for decreased power consumption. All unused inputs are tied to either Vcc or ground through resistors—this prevents unused inputs floating to any voltage and causing excess power drain. The READY input pin is tied high, thereby disabling wait-state generation; all bus accesses are zero-wait state. The EA pin is tied low to enable addressing of the external EPROM. When the power supply is first switched on by the power control circuit, the reset generation circuit holds the CPU RESET pin low for at least 20 ms, then allows the internal pull-up resistor to bring it high; this assures a good CPU reset. An internal watchdog timer is enabled and runs continuously. The watchdog timer provides a means of recovering from a software upset caused by ESD, EMI, etc. If the software does not clear the timer at least every 64K state-times (13.1 ms), the CPU will drive RESET low, resetting the entire unit. The reset output by the CPU is only 16 state-times long (3.2 µs). Q22 provides isolation from C65 so the CPU can drive a good reset to the display control circuit.


Analog Reference Voltage

Ambient Light

Battery Voltage

Ambient Temperature Analog

Battery Power

Serial Interface

CPU Power Off

Control

Patient Sensor

SpO2 Analog Section

Analog Control

Address Decoding

AD Bus

Address Demultiplexing

s s e r d d A

AD Bus Enables

Output Port

Input Port

Power Control

CPU Memory

n O r e w o P

Power Control

Power Supply

Standard User Supply


The N-20 CPU is configured as follows: • • •

• • • • •

Decoded AD0 and BHE generate separate WR write strobes for the low and high bytes of a word. The signal WR (pin WRL) is the low-byte write strobe. A standard address latch enable (ALE) is generated and used. HSO pins 4 and 5 are configured as outputs. The HSO is used to generate stable timing control signals to the SpO2 analog section, display, and printer. The timer-2 external control pins T2CLK, T2RST, T2U-D, and T2CAPT are disabled via software and used as standard I/O. The HOLD, HLDA, and BREQ bus accessing is disabled via software and the pins are used as standard I/O. Pins HSI0 and EXTINT are configured for interrupt input. The CPU receives 2 external interrupts (signals PR_TACH and PHOTOI). RXD and TXD are configured as a standard asynchronous serial transmitter and receiver for the serial interface. PWM0, PWM1, and PWM2 pins are configured as pulse width modulator outputs. They are used to control gains within the SpO 2 analog section.

9.10.9.1 Address Demultiplexing

The address demultiplexing circuit is illustrated in Figure 9-15. U13 and U33 are transparent latches that latch the address portion of the AD bus data on the falling edge of ALE; the outputs are always enabled. The outputs of U13 and U33 are always the address portion of the AD bus.


9.10.9.2 Address Decoding

The address decoding circuit is illustrated in Figure 9-16. EXINEN EXOUTEN

TO: N-20

U28 WR RD

A10

A B C

6 4 5

G1 G2A G2B

Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7

15 14 13 12 11 10 9 7

AUX PCB DC00-DFFF

74HC138

A12 A13 A14 A15

U30A 1 2 13

12

E000-FFFF RAMEN

74HC10

TP74

U30B A14 A15 A11

3 4 5

U30C 6

9 10 11

8

74HC10 TP71

20 20 HDR

ADDRESS DECODING 1 2 3

19

74HC10

0000-DBFF ROMEN


results. Due to the CPU configuration, the write strobe WR (WRL pin) is only active for low-byte writes; therefore, both bytes of the external output port must be written to at the same time. The upper byte of the output port cannot be written to alone, no write strobe and, therefore, no EXOUTEN signal will be generated. U30C generates the EPROMs active low enable signal, ROMEN. The active low signals RAMEN and EXINEN are basically used as EPROM disable signals. When RAMEN or EXINEN or test point TP71 are low, the output of U30C, ROMEN, is forced high, disabling the ROM. Therefore, the EPROM is disabled for the range DC00-FFFF and enabled for the 55 Kbyte address range of 0h-DBFF. TP71 is used during board testing to disable the EPROM. 9.10.10 CPU Memory

The CPU memory circuit is illustrated in Figure 9-17.

8K X 8 SRAM U14 A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12

10 9 8 7 6 5 4 3 25 24 21 23 2

A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12

D0 D1 D2 D3 D4 D5 D6 D7

11 12 13 15 16 17 18 19

VCC

AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7


U14 is a standard 8K ×8 static RAM. Test point TP 43 is used during testing to disable the output. The program that the CPU runs is stored in U15. U15 is a 16-bit wide output, one-time programmable (OTP) EPROM. During 16-bit wide bus accesses, the CPU uses address line A0 for low/high byte selection, and address line A0 is not used as a normal address line. The CPU can address only 64K ×8 bytes or 32K ×16 bytes. Pin A15 of U15 is tied low, always selecting the lower half of the EPROM. Signal ROMEN is then used to enable the EPROM for the proper memory area. 9.10.10.1

Input Port

The input port circuit is illustrated in Figure 9-18. EX_IN INPUT PORT U16 AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7

19 18 17 16 15 14 13 12

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8

D1 D2 D3 D4 D5 D6 D7 D8 C OC

EXINEN

2 3 4 5 6 7 8 9 11 1

GO_BTN ON_OFF_BTN DD_BTN ADV_BTN PR_HOME BAT_TYPE RTC_IO

VCC

74HC573

Figure 9-18: Input Port Circuit


9.10.11 Real-Time Clock (RTC) and Non-Volatile Memory

The real-time clock circuit is illustrated in Figure 9-20. The RTC has two functions: (1) it provides non-volatile memory that is used to remember whether the printer should be enabled at power on, and (2) to keep track of time and date for the N-20P printer. The N-20 does not require or use the RTC; it is disabled via software.

REAL TIME CLOCK

VCC

CR22 1N914

TP86 TEST

U29 TP76

16 3 5 8

TEST CR23 C114 .1uF

1N914

R163 3.32K

BT1 3V

Y1

32.768KHz

VCC X1 X2 GND DS1202S

SCLK I/O RST

14 12

RTC_CLK RTC_IO

9

RTC_RST

TP85 TEST TP87 TEST


BEEP_1 BEEP_2

BZ1 TP74

TP75 TEST

TEST

AT17 BEEPER

Figure 9-21: Audio Output Circuit BZ1, a piezo ceramic sounder, is the audio output device. Due to its low drive current of 2 mA maximum, no drive circuitry is needed, and the audio output device is driven directly from the external output port. It is differentially driven with 2 square waves 180 degrees out of phase. The drive frequency is approximately 1480 Hz or 740 Hz and is generated by the CPU. BZ1 is differentially driven to obtain maximum audible volume. 9.10.13 Display Control Circuitry

The display control circuit is illustrated in Figure 9-22, at the end of this section. The Taliq display is controlled by the display control circuitry. A photosensor measures ambient light and automatically switches on the electroluminescent display backlight during low light conditions. The display control circuitry is divided into the following subsections: 9.10.13.1 Control Conditioning Circuit


9.10.13.4 Control Conditioning Circuit

The CPU generates a 400-µs low-pulse train at a 160 Hz rate on signal DISP_PHASE. Half of U34 takes DISP_PHASE as an input and creates DISP_POL as an 80 Hz 50% duty cycle square wave. A CPU reset initializes DISP_POL low when any CPU reset occurs so the software knows the initial state. The other half of U34 is used to synchronize the rising edge of the DISP_DL with the rising edge of DISP_POL. The CPU brings DISP_LATCH signal high before the rising edge of DISP_PHASE; this allows the high to be clocked out to DISP_DL on the rising edge of DISP_PHASE. About 100 µs after the rising edge of DISP_PHASE, the CPU brings DISP_LATCH low, asynchronously resetting DISP_DL low. 9.10.13.5 Display Driver Control Circuits

U19 and U20 are the display segment driver chips. Each chip has 32 high-voltage outputs and a display common marked BP (backplane). The display data are input to U19 and U20 by the CPU via a serial shift register input. U19 and U20 are daisy-chained together, forming a 64-bit s erial shift register. Display data are loaded and shifted down via the DISP_DATA and DISP_CLK signals. When all 64 bits of the shift register are loaded, a high pulse on DISP_DL updates the display, all 64 bits at the same time. The display is clocked with an 80 Hz 50% duty cycle waveform by signal DISP_POL. The display cannot be driven by DC voltages or display damage will result. Display segments are illuminated by creating a 180-degree phase shift between the segment pin and the BP common pin. Segments are left dark by making the waveform on the segment pin be in phase with the BP pin. The display has an electroluminescent (EL) backlight, and is driven the same as the display segments. Connectors JP2, JP3, and JP5 connect the display and EL backlight to the drive electronics.


VCC TP72 GO BTN R102 15K

TEST

To U21 pin 4

GO_BTN

TO: N-20 MAIN PCB

R78 150K

R79 3.32K

JP18 1

VCON

C66 .01UF

L11

GO_SW

2 C123

TP71 TEST

100PF

VCC

CHECK BATTERY

R71 150K TP88

R74

TEST

1K

SW1

L12

BAT_BTN

TP81 TEST

C126 100PF

C64 .01UF


• •

•

•

Batteries —Four 1.5-V alkaline "C" size batteries provide 4-6 VDC power. Power control circuitry —Power control circuitry is connected to the batteries. It senses any press of the Measure button and switches on the power supplies. Reverse current limiting protects the N-20/N-20P from damage if batteries are inserted incorrectly. Power shutoff circuit—This circuit controls power to all circuits except the power control circuit. In addition, a fuse protects the power supply from excessive current draw. The power supply is also protected against electrostatic discharge and electromagnetic interference. Power supply circuits consists of the following power supplies: Regulated power supply: Power supplied by the batteries is regulated at 5 VDC. All of the digital circuitry and some of the SpO2 analog circuitry use this supply. Unregulated power supplies: 5 VDC is converted by a switched capacitor network into unregulated power supplies of –5 VDC, 10 VDC, and 12 VDC, all of which are used in the SpO2 analog circuits. High voltage power supply: A voltage regulator/doubler converts battery power to 70 VDC; the display drivers as well as the display backlight need this increase in power.

The power supply circuit is illustrated in Figure 9-24, at the end of this section. 9.10.15.1 Power Control Circuitry

The power control circuit is illustrated in Figure 9-25, at the end of this section. The power control circuit consists of U21 and its associated components. U21 is a D flip/flop with asynchronous preset and clear; only the preset and clear are used.


Q15 part 1 controls the power supplies. When a logic high is placed on the gate (pin G1) signal, PWR_ON battery ground is connected to the circuit and switched to ground via Q15 parts 1 and 2. When the power control circuitry pulls PWR_ON low, switched ground switches to a high impedance state. This action switches off the power supply and, therefore the unit, except for the power control circuit. 9.10.15.3 Vcc Power Supply

Refer to Figure 9-24, "Power Supply Circuit,” at the end of this section. The Vcc power supply is a switched inductor voltage regulator operating in boost mode (U22). The power input is provided by the batteries (VBAT). NFET (Q17) operates as a linear post regulator. The 1 M resistor (R77) operates as a static bleed device across the switched regulator when the regulator is switched down. The regulated output is Vcc (5 V ± 5%). 9.10.15.4 Raw Power Supplies

Refer to Figure 9-24, "Power Supply Circuit,” at the end of this section. The input to the raw power supplies is Vcc, which is a switched-capacitor voltage converter operating in separate multiply and invert modes in conjunction with supporting circuitry. U23 inverts Vcc and outputs raw –5 V. Raw 10 V is derived by voltage doubling Vcc with CR14, CR19, CR20, and CR78. Raw 12 V is derived by voltage tripling Vcc with CR15, Q8, Q9, C96, C81, R119, and R120. The raw power supplies are used as bias supplies for the SpO2 analog section and are not tightly regulated. The normal operating range of the raw power supplies are:


VREF TP60 U32

R123

2 4

RAW10V 182

VIN GND

C95 22UF

VOUT TRIM

6 5

LT1021

R124 1

C12 22UF

C6 0.1UF

TP70 GND

R161 Q23 2N3904

10K

+5.7 VREF

Q24 2N3904

+12V R121 TP61

RAW12V 221

C91 22UF

C80 0.1UF

-5V R122 TP62

RAW-5V 221 C94 0.1UF

C93 22UF

Figure 9-26: Analog Reference Voltage Circuit


TEMP SENSOR U5 VCC

1

VCC 2

TEMP 3

PR_TEMP

GND

C115 0.1uF

LM35

Figure 9-28: Ambient Temperature Circuit U5 is a precision-temperature sensor. It outputs (PR_TEMP) a voltage proportional to the ambient temperature, which is 10 mV per degree centigrade. For example, at a room temperature of 25 °C, the U5 output would be 250 mV. U5 is used whenever an optional printer is installed. Because the printer is a thermal printer, ambient temperature must be compensated for. 9.10.19 Battery Voltage

The battery voltage circuit is illustrated in Figure 9-29. VBAT

BATTERY VOLTAGE SENSE

TP73

R69 15.8K 1% BAT_VOLT R70 47.5K 1%

C62 .01UF


the battery and the VRECHARGE terminals are mechanically connected. This applies the battery voltage to VRECHARGE, pulling BAT_TYPE high. R100 and CR27 are a current-limiting resistor and a voltage-clamping diode that are used to protect the input port from excessive battery voltage. If disposable batteries are used, VRECHARGE is electrically isolated, which allows R101 to pull BAT_TYPE input low. The nominal voltages and voltage discharge curves are significantly different between rechargeable and disposable batteries. In order for the CPU to predict how much "battery life" remains, the nominal voltage and discharge curves must be known; the BAT_TYPE signal provides that information. 9.10.21 Printer Control

Printer circuitry is divided into two subsections: the printer interface and the printer flex circuit. Printer interface circuitry is present on both models, but is disabled by software in the N-20. •

•

Printer interface circuit (auxiliary PCB)—This circuit detects the presence of the flex circuit, and supplies power to the print heads and paper-advance motor. Noise generated by the printer motor is filtered. The circuitry is protected from excessive battery currents by a fuse. The printer interface circuit is illustrated in Figure 9-31 (at the end of this section). Printer flex circuit (N-20P only)—The printer flex circuit is added when the printer is present. The printer generates a timing signal that is read by the CPU and sent to the flex circuit. This circuit signals the CPU that a printer is present by connecting one CPU input to ground. Power and power control signals from the auxiliary PCB generate an output load for a resistor array; heat from this process produces a dot matrix pattern on thermal paper. The printer flex circuit is illustrated in Figure 9-32.


SEIKO MTP102-16 PRINTER

TO N-20 AUX BOARD JP9

VPRN

JP10

TG

M+ MTG

HM

HM

1 2 3 4 5

HEADER 6 DOT4 U1

6 7 8 9 10 11 12 13

1 2 3 4 5 6

PR_DOT3

8 1 2 3 4 5 6 7

PR_DOT2

10

PR_DOT6 PR_DOT5 PR_DOT4

PR_DOT1

C3 PR_MOTOR

OUTM OUT0 OUT1 OUT2 OUT3 OUT4 OUT5 OUT6

VCC

GND

LB1256

PR_DOT0 3300UF

JP11

INM IN0 IN1 IN2 IN3 IN4 IN5 IN6

11 18 17 16 15 14 13 12 9

DOT6 DOT5 DOT4 DOT3 DOT2 DOT1 DOT0

8 7 6 5 4 3 2 1 HEADER 8


The N-20 is configured in two ways, with printer and without printer. The following is a description of the printer interface circuitry found on all N-20 auxiliary PCBs. The printer interface circuitry is there regardless of the unit configuration; however, if the optional printer is not installed, this circuitry serves no function. The CPU reads the PR_PRESENT signal to determine if a printer is installed. With PR_PRESENT left floating, it is pulled high by the weak pull-up resistor inside the CPU. If a printer is installed, PR_PRESENT is connected to switched ground, which causes a low input to the CPU. The optional printer circuit is protected from excessive battery currents by fuse F2. CR28 is used to block noise generated by the printer motor being injected onto the batteries. The N-20 printer is a 16-character–wide thermal dot matrix printer, which generates a CPU interrupt for every dot column. The thermal energy given to the print head is controlled by the pulse width of the active high signals PR_DOTx. In order to provide consistent print quality, the ambient temperature, print drive voltage, and print head resistance must be measured and accounted for. Inside the print head are seven resistors that heat up when power is applied, and in turn create dark dots on the thermal paper. One lead of the print-head resistors is connected to the printer supply voltage VPRN; the other lead is connected to the driver chip (see Optional Printer Flex Circuit with User Controls). One of the print dot resistor leads (DOT4) is also fed back to the printer interface circuitry. The DOT4 signal is a print dot resistor with a range of 11–16 ohms, which is connected to VPRN. The print head resistance is measured by U36. A two-level resistor bridge is formed by R143, R144, R145, R146, and head resistor DOT4. The resistor bridge is switched on when PR_MEAS is pulled high, pulling TP77 low and biasing the resistor bridge. The logic outputs of PR_HEAD1 and PR_HEAD2 are read in by the CPU to determine which of the three head resistance categories this


PWR_ON is high, the sources (S1, S2) short to the drains (D1, D2), connecting ground to U1 and C3. PWR_ON also controls the regulated power supplies; thus, Q1 and the power supplies are both enabled and disabled at the same time. The large bulk capacitor C3 is required due to the large current spikes that are required by the printer and the large internal series resistance of disposable batteries. Bulk capacitance is required to lessen the drop in battery voltage caused by the current spikes. The N-20P has three additional user-control buttons. L8, L9, L10, C120, C121, and C122 provide ESD protection. R103, R104, and R105 provide pull-ups when the user buttons are open. These pull-up resistors are in the printer interface circuit to ensure that the buttons (ON , ADV , and D/D) are never left floating, regardless of whether an optional printer flex circuit is installed or not. The optional user controls consist of three momentary push-button elastomeric contact switches. Pull-up resistors are provided by the printer interface circuitry. R1, R2, and R3 help protect the input port by providing some current-limiting capability. C4, C5, and C6 debounce the switch contacts.

9.11

Support Illustrations

These illustrations, at the end of this section, support the descriptions within this manual. Figure 9-8: LED Drive Circuit Figure 9-9: Differential Synchronous Demodulation Circuit Figure 9-10 N-20 HSO Timing Diagram

VCC

SENSOR INPUT

PWM1

LED DRIVE

C55

P1

TP45

4

R46 10K

.1UF

VREF 5 9 8 3 7 2 6 1

PWM2

Q3 MMBTA56

VCC

R45 Q4 MMBTA56

L3

13 2 1

L4 L5

R64 C116

C117

C118

100PF

100PF

100PF

5 3

10K

DB9F

Q1

TP46

TP47

MMBTA06

R48 10K

6 11 10 9

TP50 C119

X0

X

X1 Y Y0 Y1

Z

14 15 4

R135

6 U9A

R42

3.74K 1

4.7PF

280K

7 8

LT1013

TP83 2

R53

Z0 Z1 VSS INH A B

VEE

C

VDD

100K

8 7

C53

16

.1UF

C36

R43 20K

.1UF C39

4053

R51

VREF

C60

U10 12

10K

VCC

R50 182K

.022UF TP84

R52

100PF

TP48

22.1K

R54

100K

C37

6.8

.1UF

Q2

R18 6.04K

MMBTA06 RSENS

R44 20K

C38 R47 10K

Q5 2N3904

TO CENTER MTG. HOLE

TP77 .022UF

C5 .01UF

C123

22PF

PHOTOI IR/RED

IR/RED R49 100K R162 100K

CR12 OFF/ON 1N914 CR18 LED DIS 1N914 RSENS

Figure 9-8 LED Drive Circuit

TP78 R159

VREF

88.7K .1%

+12V

R63 2.0K

7

5

2 R160

U35 6

3

LT1097

51.1K R23

R158 88.7K .1%

SAMPRED SAMPIR OFF/ON

4 1 8

1M

-5V

8 6

7 U6D LTC201 U1D

12

VREF

14 13 LF444 C40

R2

390PF

1M

R17 3.32K

C1

1

TP49 3

18PF +12V R1

4

182K

3

U1A 9

R58 3.32K

11

R19 280K

RED

C24 .47UF

C59 .047UF VREF

2

U6C 10 LTC201

1 1 -5V

VREF

1 6

R157 511K C22 .047UF

14

15 U6B LTC201

R27

IR

3.32K C25 .47UF

TP44

SENSOR INPUT

82.5K

3.32K

1 LF444

VREF VREF

R57 40.2K

P1 5 9 4 8 3 7 2 6 1

R26

2 U6A LTC201

L1

U9B

R56

3 5

15.8K

4

PHOTOI

LT1013

TP79

DB9F

Figure 9-9 Differential Synchronous Demodulation Circuit

OFF/ON (HSO.1)

/SAMPIR (HSO.2)

/SAMPRED (HSO.0)

IR/RED (P1.1)

-60µS

-60µS

µS

0

105.6

State Time

0

66

158.4 177.6 99

111

283.2 177

336.0 337.2 210

211

443.2 277

496.0 515.2 310

322

620.8

673.6

388

421

Figure 9-10 N-20 HSO Timing Diagram

VCC

LTC201 5 U11B

LTC201 2 U11A 1

16

REDLED/AV

3

1 4

From U2 pin 3

IRLED/AV R20

REDDC

3.32K +5.7

R67

4 U7A

R29

1 2

REDAC

+

3.32K

LMC6044

C9 .015UF

TP54

.01UF

3.32K

3 RED

C7 .01UF

C61

C26 .1UF

C28 1NF

1 1

C27 .47UF

TP55

R30 100K

11 U11C LTC201

9

R28

10 R22

34.8K

VREF

12.1K

3.32K

2 1

U7C

10

5 3

8 9

R41 15K

6 11 10 9

R40 47.5K

LMC6044 TP85

C56 .01UF

U3 12 13

R60

X0 X1

X Y

Y0 Y1

Z

Z0 Z1

14 15 4

PWM1

TP56 VSS

INH A B C

VEE VDD

8 C58

7

.1UF

16

TP57

4053

VCC

R36

REDLED/AV PWM0

100K

IR

R21 C111 C29 .015UF

U7B

5

6 U11D LTC201

6

3.32K

LMC6044

+

C30

C31 .47UF

.1UF

7

C57 .01UF

C32 R31

C8 .01UF

R33

7 8

IRDC

3.32K

R66 3.32K

.01UF

VREF

TP58 IRAC

TP59

R61 3.32K

1NF

12.1K

/ZERO

R37 34.8K

13

TP76

U7D

BUS TO CPU

14 12 LMC6044

R5 15K

TP86

Figure 9-13 AC Variable Gain Control Circuit

EX_OUT LSB U18 AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7

2 3 4 5 6 7 8 9

EXOUTEN

11 1

R132 150K

D1 D2 D3 D4 D5 D6 D7 D8

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8

19 18 17 16 15 14 13 12

DISP_DATA DISP_CLK RTC_CLK RTC_RST PR_MOTOR PR_MEAS BEEP_1 BEEP_2

CLK OC 74HC574

TP82 TEST EX_OUT MSB U17 AD8 AD9 AD10 AD11 AD12 AD13 AD14 AD15 EXOUTEN PR_STROBE R123

2 3 4 5 6 7 8 9 11 1

D1 D2 D3 D4 D5 D6 D7 D8

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8

CLK OC 74HC574

19 18 17 16 15 14 13 12

PR_DOT6 PR_DOT5 PR_DOT4 PR_DOT3 PR_DOT2 PR_DOT1 PR_DOT0 RTC_IO

R148 R149

150K

VCC 150K

R150

150K

150K

R151

150K R152 150K

R153

R 15 4

1 50 K

150K

Figure 9-19 Output Port Circuit

DISP_POL

DISPLAYDRIVERS VCC

DISP_DL

U19 24 VDISP 28

VDD

VPP

TP80 TEST DISP_DATA

27

DISP_CLK

25 23 22 18 26

VCC

20 21

19

DIN CLK LATCH POL DOUT SL

OSCIN OSCOUT

GND

JP2 O1 O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O19 O20 O21 O22 O23 O24 O25 O26 O27 O28 O29 O30 O31 O32 BP

17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

+70V DISP_PHASE R93 182 1%

+70V TALIQ COLDSWITCH R113 4.75K

Q14 MMBT5401L VCC C87

R115

Q13 2N3904

475K

R117 6.19K

24

28

27 25 23 22 18

VCC

26

20 21

19

VDD

VPP


OSCIN OSCOUT

GND

O1 O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O19 O20 O21 O22 O23 O24 O25 O26 O27 O28 O29 O30 O31 O32 BP

17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30

390PF Q21 MMBT5551L

R114 12.1K

HDR32 R95 182 1%

JP3 U20

390PF C83

SI9530 VCC

VDISP

R116 10K Q12 MMBT5551L

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

DISPLAY PS CTRL U34

RST

10 12 11 13

HDR32

29

VCC

SI9530

4 2 3 1

14

SET1 D1 CLK1 RST1

Q1 Q1

SET2 D2 CLK2 RST2

Q2 Q2

VCC

GND

5 6

DISP_POL

9 8

DISP_DL

7

74HC74

EL DRIVE JP5 1 2 3 4 5 6 7 HDR7

Figure 9-22 Display Control Circuit

BATTERY INPUT BATTGND

TP3 TOCENTERMOUNTINGHOLE

TEST

BATTPLUS

R155 10K

TP1

F1

TEST

1.5A

POWER SUPPLY VBAT

R77 Q17

1M Q15 4 3 2 1

G2 S2

D2 D2

G1 S1

D1 D1

5 6 7 8

CR24 TRANZORB

C73 0.1UF

C116 22UF

C117 22UF

C74 22UF

R134 L1

150

U22 1 2

120UH

10V

3

SI9956DY

4 CR13

ILIM VIN

AO

SW2

GND

R82 100K

7

SET

SW1

2 3

8

FB

R84 10K

4

6

SRC SRC

8 7 6 5

DRN DRN DRN DRN

GATE

C76 100PF VCC

R85 100K

SI9405DY

C71 22UF

C72 .1UF

5

LT1173

130T3 C75 0.1UF

C70

C118

C119

22UF

22UF

22UF

R86 31.6K

R83 28.7K

RAW-5V

CR19

130T3

C78

CR20

+

U23 14 13 12 11 C82 22UF

R120

V+

FB/SD

OSC

CAP+

VREF

GND

VOUT

CAP-

3

.47UF

22.1K

RAW10V 130T3

C125 22UF

CR14 130T3

2N3906

4 5

Q9

C81

Q8

.1UF

CR15

C96 2.2UF

6

LT1054CS

R119

RAW12V 130T3

C79 22UF

2N3904

C90

TP38 TEST

22UF

C112

CR31

MURS110 +70V

U26 5 L2 120UH

6 7 8

1UF 50V

CR30 MURS110

VIN E1

FB

VSW

VC

E2

GND

CR16

3 2 1

3.32K C85

LT1172

MURS110

R96 CR25 5367A 43V10% 5W

C113 4.7UF 50V

C92 2.2UF 50V

C95 2.2UF 50V

R125 390K 1%

R126 390K 1%

C124 .1UF 100V

0.1UF R127 14K 1%

Figure 9-24 Power Supply Circuit

Q15

2 3

6

8

VCON

LT1046

CR11

TP84 VCC

VBAT

TEST TP72

R102 15K

TEST

1N914 C68 0.1UF

VCON

VCON U21

GO_BTN

TO: N-20 MAIN PCB

R79 3.32K

JP18 1

4 2 3 1

R78 150K

C66 .01UF

L11

10 12 11 13

VCON

GO_SW R110 475K

2 C123 3 100PF

4

TP71 TEST

Q1 Q1

SET2 D2 CLK2 RST2

Q2 Q2

5 6

PWR_ON

TP83 TEST

VCC

GND

9 8

GO BTN

7

R81 74HC74 3.32K

C110 C67 0.1UF

5

14

SET1 D1 CLK1 RST1

TP73 TEST

0.1UF JP9 PIN 17

6 7 8 9

PWR_DOWN

Figure 9-25 Power Control Circuit

ON BTN DD BTN ADV BTN PR_PRESENT VPRN

11

U36B 13

PR_HEAD1

R143 14.0K

12

LT1017CS

TP78 TEST VPRN R144 1.24K

R146 1 4

VPRN

R106 150K PR_TACH VCC

R145 60.4K TP77 TEST

6

Q20 2N3904

R142 150K Q19

TO PRINTER PCB TP35 TEST

TP36 TEST

TP37 TEST

JP9 VPRN

CR29

C127

TG

100pf

HM

1N914

2N3904

R118 150K

1 2 3 4

R141

PR_HOME PR_MEAS

TP79 TEST

4

LT1017CS

VCC

59 5

U36A 3

PR_HEAD2

DOT4

1K

R147

VPRN 3.32K

PR_DOT6

R156 1K

PR_DOT5 PR_DOT4 PR_DOT3 PR_DOT2 PR_DOT1 PR_DOT0 PR_MOTOR

5 6 7 8 9 10 11 12 13 14 15

TP24 TEST

TP27 TEST

TP23 TEST

TP30 TEST

TP26 TEST

TP29 TEST

TP25 TEST

VPRN

16

PWR_ON

17

TP28 TEST

18 PR_PRESENT

L8

R104 VCC 150K

R103

L9

150K

L10

VCC R105 VCC

ON_OFF

20

ADV

21

DD

22

150K

22 HDR TP31 TEST

CR28

F2

130T3

1A

19

VBAT

VPRN

C122

C121

C120

100PF

100PF

100PF

TP32 TEST

TP34 TEST TP33 TEST

C115 0.1UF

Figure 9-31 Printer Interface Circuit

SAMPIR SAMPRED PWM1 AC + DC

Input Signal Conditioning

Signal Gain

AC Ranging

/ZERO PWM0

RED

Zeroing r e t r e v n I

and Current to Voltage Conversion

Offset Subtraction

Variable Gain and Filter

REDAC PWM2

DMUX

CPU PWM0 IR

Sensor



Offset Subtraction


IRAC

AC + DC RSENS /ZERO IR/RED

RED IR

LED Drive

OFF/ON LED DIS PWM0, PMW1, PWM2

Output

Figure 9-33 N-20 SpO2 Analog Block Diagram

CPU

VREF U31

REDDC REDAC IRDC IRAC RSENS AMB_LIGHT BAT_VOLT PR_TEMP PR_TACH

ALE RD WR AD15 AD14 AD13 AD12 AD11 AD10 AD9 AD8 AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0

13 12 6 5 7 4 11 10 8 9 15 14 VCC 37 62 61 40 41 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

VREF ANGND ACH0/P0.0 ACH1/P0.1 ACH2/P0.2 ACH3/P0.3 ACH4/P0.4 ACH5/P0.5 ACH6/P0.6 ACH7/P0.7 EXTINT/P2.2 GND VPP ALE/ADV RD WRL/WR WRH/BHE AD15/P4.7 AD14/P4.6 AD13/P4.5 AD12/P4.4 AD11/P4.3 AD10/P4.2 AD9/P4.1 AD8/P4.0 AD7/P3.7 AD6/P3.6 AD5/P3.5 AD4/P3.4 AD3/P3.3 AD2/P3.2 AD1/P3.1 AD0/P3.0

T2CLK/P2.3 T2RST/P2.4 P2.6/T2U-D P2.7/T2CAPT HSI0 HSI1 HSI2/HSO4 HSI3/HSO5 HSO0 HSO1 HSO2 HSO3 P2.5/PWM0 P1.7/HOLD P1.6/HLDA P1.5/BREQ P1.4/PWM2 P1.3/PWM1 P1.2 P1.1 P1.0

44 42 33 38 24 25 26 27 28 29 34 35 39 32 31 30 23 22 21 20 19

PR_HEAD1 PR_HEAD2 REDLED/AV /ZERO PHOTOI DISP_PHASE PR_STROBE SAMPRED OFF/ON SAMPIR PWM0 PR_PRESENT IRLED/AV PWR_DOWN PWM2 PWM1 DISP_LATCH IR/RED LEDDIS 10K

READY INST BUSWIDTH NMI CLKOUT RXD/P2.1 TXD/P2.0 EA RESET XTAL2 XTAL1

43 63 64 3 65 17 18 2 16 66 67

80C196KC

R131

RST

VCC

RAMEN NMI TP4

RXD TXD EA RST

R76 10K

C88

22PF C89

R137 10K

R75 10K

Y2 10MHz

22PF

RESET GENERATION VCC

VCC

R72 100K

TP41

C65 .1UF TP42

RST

R73 15K CR10 1N914

Q22 2N3904 R156 15K

Figure 9-34 CPU Circuit

LIGHT SENSOR TO: N-20

VCC

SpO2 ANALOG

DIGITAL SECTION

VCC D8 VTB8442B

AUX PCB R80

JP8 GO_SW

Q8 MMBTA13L

TP78

+12V

R159 VREF

88.7K .1%

+12V R63 2.0K

7

C125

.1UF TANT ACROSSU35 -5V SUPPLY

U35

3

R23

R158 88.7K .1%

1M

.1UF

C21 22UF TANT ACROSSU6 SUPPLY

-5V -5V

-5V

C35

7

.1UF

8

C1 18PF

TP49

R19 280K

4 U1A

11

R58 3.32K

3

L-8

DB9F

R26

2 U6A LTC201

Q6 C33 1NF

1 1

LF444

14

C24 .47UF

R46 10K

.1UF

VREF

R27

15 U6B LTC201

C1 18 100PF

100K

C14 TP89

MMBTA06

5 3 6 11 10 9

TP50

VREF

3 1 3

X0 X1

X Y

Y0 Y1

Z

Z0 Z1 VSS INH A VEE B C VDD

14 15

U9A

1

3.32K

LT1013

2

U4B

C111 .01UF C29 .015UF

C36 .1UF

C20

R43 20K

.1UF .022UF

8

VSS INH A VEE B C VDD

C58

7

.1UF

16

TP57

R5 15K

13

R123

2 4

RAW10V 182

C95 22UF

VIN GND

VOUT TRIM

6 5

LT1021

R124 1

C12 22UF

C6 .1UF

1N914

100K

1N914

TP70 GND

U7D

R57 40.2K

14

TP76

LMC6044 TP86

U9B

R56

2 3 4 5 6 7 8 9

3 5 4

PHOTOI

ALE

LT1013

11 1

TP39

10K Q24 2N3904

VREF

+5.7

C51

C52

.1UF

.1UF

.1UF

C48 22UF

C49 22UF

AD8 AD9 AD10 AD11 AD12 AD13 AD14 AD15 TP73

C102

C105

C1 06

C 10 7

C108

C109

.1UF

.1UF

.1UF

.1UF

.1UF

.1UF

R69 15.8K 1% BAT_VOLT

BATTERY VOLTAGE SENSE

R70 47.5K 1%

C62 .01UF

TP64 C91 22UF

C80 .1UF

TEMP SENSOR VCC

RAW-5V

1

VCC TEMP

TP62 221 C94 .1UF

C93 22UF

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8

19 18 17 16 15 14 13 12

16

Q2 Q2

17

VCC

GND

18 19 20

7

20HDR

74HC74 RAMEN NMI TP4

RXD TXD EA

TP66 VCC RST

L6

TXD RXD

TP65

R128 10K

JP1

BEAD L7

R75 10K

1 2 3 4

BEAD

SERIAL DATA PORT

4HDR

C121

C120

100PF

100PF

AD15

A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12

74HC573 R108 10K

3

GND LM35

2 3 4 5 6 7 8 9 11 1

D1 D2 D3 D4 D5 D6 D7 D8

RAMEN

C OC 74HC573

19 18 17 16 15 14 13 12 TP5 TP6 TP7 TP8 TP9 TP10 TP11 TP12 TP13 TP14 TP15 TP16 TP17 TP18 TP19 TP20

2

PR_TEMP

A8 A9 A10 A11 A12 A13 A14 A15

10 9 8 7 6 5 4 3 25 24 21 23 2 20 26 27 22

WR RD Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8

VCC

VCC

3 4

AD13

5

U14

A0 A1 A2 A3 A4 A5 A6 A7

C OC

TP21 TP22

U5 -5V R122

D1 D2 D3 D4 D5 D6 D7 D8

R109 10K

TP61

221

ALE TP40

+12V R121 RAW12V

SET2 D2 CLK2 RST2

8K X 8 SRAM

U33

RSENS

Q23 2N3904 C50

DISP_DL

15

2


VCC

C11 22UF

9 8

14

VCC

1

LEDDIS

TP63

DISP_POL

JP7

ADDRESS DEMUX

VBAT R161

14

VCC

5 6

13

VBAT

10 12 11 13 VCC

Q1 Q1

RESET GENERATION

OFF/ON CR18

RST

SET1 D1 CLK1 RST1

12

RAW-5V

TP59

22PF

R162

U34 4 2 3 1

Y2 10MHz

IR/RED

100K

11

RAW12V

22PF

IR/RED

TP60

TALIQ PS CTRL

IRAC

C31 .47UF

TP80

CR12

R137 10K

RAW10V

TP58

+

C30

TP79

R49

10

DISP_DL

PWM0 PR_PRESENT IRLED/AV PWR_DOWN PWM2 PWM1 DISP_LATCH IR/RED LEDDIS R131

9

DISP_POL

R76 10K

22PF C89

12

.022UF

VREF

7

DISP_PHASE

DISP_PHASE PR_STROBE SAMPRED OFF/ON SAMPIR

10K

IRDC

VREF R37

R44 20K

PR_HEAD1 PR_HEAD2 REDLED/AV /ZERO PHOTOI

43 63 64 3 65 17 18 2 16 66 67

READY INST BUSWIDTH NMI CLKOUT RXD/P2.1 TXD/P2.0 EA RESET XTAL2 XTAL1 C88

/ZERO

TOCENTERMTG.HOLE

U32

VPP ALE/ADV RD WRL/WR

REDLED/AV PWM0

C8 .01UF

44 42 33 38 24 25 26 27 28 29 34 35 39 32 31 30 23 22 21 20 19

T2CLK/P2.3 T2RST/P2.4 P2.6/T2U-D P2.7/T2CAPT HSI0 HSI1 HSI2/HSO4 HSI3/HSO5 HSO0 HSO1 HSO2 HSO3 P2.5/PWM0 P1.7/HOLD P1.6/HLDA P1.5/BREQ P1.4/PWM2 P1.3/PWM1 P1.2 P1.1 P1.0

VCC

1NF

15.8K C123

VREF ANGND ACH0/P0.0 ACH1/P0.1 ACH2/P0.2 ACH3/P0.3 ACH4/P0.4 ACH5/P0.5 ACH6/P0.6 ACH7/P0.7 EXTINT/P2.2 GND

R61 3.32K

TP77

C5 .01UF

13 12 6 5 7 4 11 10 8 9 15 14 VCC 37 62 61 40 41 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

AD14

TP84

C37 .1UF

6

PWR_DOWN

U13

C38 Q5 2N3904

TP56

.1UF C57 .01UF

VREF

34.8K

R47 10K

PWM1

1N914

R50 182K

100K

RSENS

4

Z

Z0 Z1

3.32K

LMC6044 C32

R31

AD15 AD14 AD13 AD12 AD11 AD10 AD9 AD8 AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0

15

Y

R33

7 6 U11D LTC201 7

CR4 12.1K

R52

MMBTA06

X

Y0 Y1

3.32K

R66 3.32K

U7B

5

6

1N914 TP90

C39

VCC

X0 X1

R21

8 .068UF

C53

16

6 11 10 9

R40 47.5K

CR2

TP83

R53

ALE

C56 .01UF

14

100K

VREF

100K

7

5 3

LMC6044

OP490SO R42 280K

7

8

2 1

5

8 4

U3 12 13

R36

4.7PF

TP55

RD

U7C

TP85

R12 100K

C60

6

C27 .47UF

4053

Q2

R18 6.04K 0.1%

R60

34.8K

-5V 6

REDAC

WR

R41 15K

C19 .12UF

OP490SO

100K C17 .068UF

C26 .1UF

8 1

R10

R28

12.1K

22.1K

R54 6.8

TP48

10

100K

OFF/ON

4053

R51

VREF

100PF

U11C LTC201

U4A

Q25 2N3906

REDDC REDAC IRDC IRAC RSENS AMB_LIGHT BAT_VOLT PR_TEMP PR_TACH

TP54

+

100K

11

9

1N914

R22

.12UF

7

U10 12 13

R48 10K

U31

.01UF

C28 1NF

1 1

5

8

CPU

VREF

R30

CR3 1N914

4

C7 .01UF

3.32K

LMC6044

C9 .015UF

OP490SO C R 1 V RE F

+12V

LF444 R135 3.57K

2

12

100K

4

PR_PRESENT

REDDC

R29

1 10

C18

2

VCC

Q1

TP46

C119

OP490SO

TP52 R11

VREF

10K

10K

TP47

100K

.068UF

U1B

5 C25 .47UF

2 1 C 117 100PF

6

82.5K

R64 C116 100PF

1NF

3.32K

L4 L5

R8

7

Q4 MMBTA56

L3

16 14

TP51

2N3906

R24

R45

Q3 MMBTA56

TP45

R9

C15 .068UF

C127 220PF VREF

Q7

LED DRIVE

C55

U4D

100K

10

VCC

L1 L2

U1C

9

U4C

11

R7

2N3906

82.5K

1 6

C22 .047UF

TP44

.12UF

3.32K

U7A

3 15

8

C34

VREF

100K

4

3.32K

C59 .047UF

R157 511K

C126 220PF VREF

3

TP53

3.32K C61

R67

+5.7

.12UF

R25

1

2 LF444

-5V

5 9 4 8 3 7 2 6 1

TP87

R20

C16

R6

VREF

INPUT

TP88

TP81

47.5K

13 12

X1 X0

1

10

REDLED/AV

3

C13

1 2

Y X

R39

2

PR_HEAD2

PR_TACH

IRLED/AV

3 5

Y1 Y0

4053

+12V R1 182K

P1

Z

14

R2

3

U6C LTC201

INH VSS

15

1M

9 10 11 6

C B A

VEE

14 LF444

SENSOR

VDD

4

C63 .01UF

PWM2 SAMPRED SAMPIR OFF/ON

Z1 Z0

U1D

GO BUTTON

PR_HEAD1

TP75

1

16 1 4

1

221 S2

PR_STROBE

LTC201 2 U11A

OFF/ON U2

VCC

13 C40 390PF R17 3.32K

LTC201 5 U11B

C23 22UF TANT ACROSSU11 SUPPLY

4 1 8

7 U6D LTC201

12

VREF

9

VREF

.1UF

8 6

R136 33.2K

VCC

C122

16

-5V

+12V

-5V

LT1097

51.1K

TP72

R68 2.2M

6

R160

+12V

C124

5

2

+12V

A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12

D0 D1 D2 D3 D4 D5 D6 D7

11 12 13 15 16 17 18 19


C65

R72 100K

TP41

AD12

6

AD11

7

.1UF AD10

TP42 RST

R73 475K

8

AD9

9

AD8 CR10 1N914

Q22 2N3904 VCC

10

AD7

R156 475K

11

AD6

12

AD5

CS1 CS2 WE OE

R133 10K

13

AD4

14

AD3

15

AD2

16

AD1

17

TP43 AD0 A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15

ROMEN RD

64K X 16 EPROM

18 EXINEN

U15

A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 ROMEN RD VCC VCC

24 25 26 27 28 29 30 31 32 35 36 37 38 39 40 41 3 22 2 43

A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 CE OE VPP PGM

O0 O1 O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15

21 20 19 18 17 16 15 14 11 10 9 8 7 6 5 4

AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7 AD8 AD9 AD10 AD11 AD12 AD13 AD14 AD15

EXOUTEN

ADDRESS DECODING WR RD A10

A B C

6 4 5

20

TO: N-20

U28 1 2 3

19

20HDR

15 14 13 12 11 10 9 7

Y0 Y1 Y2 Y3 Y4 Y5 Y6 Y7

G1 G2A G2B

AUX PCB DC00-DFFF

74HC138 A12 A13 A14 A15

U30A 1 2 13

12

E000-FFFF RAMEN

8

0000-DBFF ROMEN

27C1024L 74HC10

TP74

U30B C115 .1uF

A14 A15 A11

3 4 5

U30C 6

9 10 11

74HC10 74HC10

TP71

NOTES: 1. ALLRESISTORS1/8W 1%UNLESSOTHERWISESPECIFIED.

10K R134 VCC

Figure 9-35 Main PCB Schematic Diagram

BATTERY INPUT TP3 BATTGND

TOCENTERMOUNTINGHOLE TEST

R155 10K

TP1

POWER SUPPLY

VBAT

F1

R77

BATTPLUS

Q17 TEST

1.5A

1M Q15 4 3

VCC CR27 1N914 TP2

G2 S2

2 1

G1 S1

5 6

D2 D2

CR24 TRANZORB 10V

7 8

D1 D1

C116 22UF

C73 .1UF

C117 22UF

C74 22UF

U22

R134 L1

1

150

2

120UH

4

VRECHARGE TEST

2 3

8 R82 100K

7

SET

SW1

AO

SW2

GND

R84 10K

SRC SRC

4

8 7 6 5

DRN DRN DRN DRN

GATE

6

R85 100K

SI9405DY

VCC

C76 100PF

C71 22UF

C72 .1UF

5

LT1173

15K R101 150K

6

FB

VIN

3

SI9956DY

R100

ILIM

BAT_TYPE

VCON C75 .1UF

TP84

2

3

C70

C118

C119

22UF

22UF

22UF

R86 31.6K

R83 28.7K

TEST LT1046

RAW-5V

C68 .1UF

8 VCC TP72 R102 15K

C78 TEST

VCON

VCON

GO_BTN

4 2 3 1

R78 150K

MAIN PCB R79 3.32K JP18

VCON

C66 .01UF

L11

10 12 11 13

GO_SW

1

+

U21

TO: N-20

R110 475K

2 3 4

PR_HEAD1

C123

PR_HEAD2

100PF

TP71 TEST

PWR_ON

14 13 TP83 TEST

SET2 D2 CLK2 RST2 VCC

12

9 8

Q2 Q2

FB/SD

OSC

CAP+

VREF

11

22.1K 4 C81 5

C96 2.2UF

RAW12V

6

CAP-

.1UF

LT1054CS

C79 22UF

R119

C90

22.1K

TP38 TEST

C112 1UF 50V

22UF JP9 PIN17

.1UF

TP73 TEST

+70V U26

PR_TACH

6

5 PR_PRESENT

7

L2 120UH

8

E1

7

VSW

8

E2

DISP_PHASE DISP_POL

11

TALIQDRIVERS

DISP_DL

12

U19 24

13

RAW10V

14

RAW12V

15

RAW-5V

16

VCC

VDISP 28

VPP

TEST

17 18

VDD

TP80

VBAT

DISP_DATA

27

DISP_CLK

25 23

19

22

20 20HDR

18 26

VCC

JP17


1 2 3 4

AD15

20

AD14

21

OSCIN OSCOUT

AD13

5

AD12

6

19

AD11

7

GND

BP

17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29

AD8

24

VDD

AD7

11

28 AD6

12

VPP

AD5

13

AD4

14

27 AD3

15

25 AD2

16

23 AD1

17

22 AD0

18

18 EXINEN

19

VCC

EXOUTEN

20

26


20HDR

TO: N-20

20 21

MAIN PCB

19

OSCIN OSCOUT

GND

C85 .1UF

R71 150K

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

TP88

R74

TEST

1K

O1 O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O19 O20 O21 O22 O23 O24 O25 O26 O27 O28 O29 O30 O31 O32 BP

17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30

C100

C101

.1UF

.1UF

C49 22UF

1 2 3 4 5 6 7

C87 390PF

VDISP

VPRN U36B

U16 AD0 AD1 AD2 AD3 AD4 AD5 AD6 AD7

19 18 17 16 15 14 13 12

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8

2 3 4 5 6 7 8 9

D1 D2 D3 D4 D5 D6 D7 D8 C OC

11 1

GO_BTN

PR_HEAD1

11

R143 14.0K

13

R115

LT1017CS R144 1.24K

R146 1 4 PR_HEAD2

59

VPRN R106 150K

PR_TACH

EXOUTEN

11 1

D1 D2 D3 D4 D5 D6 D7 D8

19 18 17 16 15 14 13 12

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8

DISP_DATA DISP_CLK RTC_CLK RTC_RST PR_MOTOR PR_MEAS BEEP_1 BEEP_2

VCC

R118 150K

TP77 TEST

R142

TOPRINTERPCB Q20 2N3904

150K

TP35 TEST

TP36 TEST

TP37 TEST

JP9

Q19

VPRN

C127

TG

100pf

HM

2N3904

DOT4

1K

R147

VPRN 3.32K

R156

PR_DOT6

1K

74HC574

BZ1

PR_DOT5 TP74

TP82 TEST

PR_DOT4 TP75 TEST

EX_OUTMSB U17 AD8 AD9 AD10 AD11 AD12 AD13 AD14 AD15 EXOUTEN PR_STROBE

2 3 4 5 6 7 8 9

D1 D2 D3 D4 D5 D6 D7 D8

11 1

TEST

PR_DOT3

AT17 BEEPER

PR_DOT2

PR_DOT6 PR_DOT5 PR_DOT4 PR_DOT3 PR_DOT2 PR_DOT1 PR_DOT0 RTC_IO

PR_DOT1 PR_DOT0 PR_MOTOR

TP24 TEST

R148

74HC574

150K

REAL TIME CLOCK

U29

TP76 TEST

16 3 5 8

CR23 C114 1N914 .1uF

R163

Y1

VCC X1 X2 GND

SCLK I/O

DS1202S

RST

14 12

RTC_CLK RTC_IO

9

RTC_RST

2 3

5 6 7 8 9 10 11 12 13 14 15

CLK OC

R123 VCC

19 18 17 16 15 14 13 12

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8

1

4

PR_HOME

CLK OC

R132 150K

R95 182 1%

R145 60.4K

6

R141

PR_MEAS

Q21 MMBT5551L

3 4

U18 2 3 4 5 6 7 8 9

R117 6.19K

R114 12.1K TP79 TEST

5

LT1017CS VCC


C83 390PF Q13 2N3904

475K

VPRN

U36A VCC

R116 10K

Q12 MMBT5551L

TP78 TEST

12 ON_OFF_BTN DD_BTN ADV_BTN PR_HOME BAT_TYPE RTC_IO

74HC573

EXINEN

VCC

JP5 VCC

C99 .1UF

Q14 MMBT5401L

VCC

PR_PRESENT

EX_ININPUTPORT

150K

R149

R150

150K

150K

R151

R152

150K

150K

R153

R154

TP23 TEST

TEST TP87 TEST

TP26 TEST

TP30 TEST TP29 TEST

VPRN

16

PWR_ON

17

TP28 TEST

18 PR_PRESENT

VCC

VCC

L8

R104 150K VCC R105

ON_OFF ADV

21

L10

150K

19 20

L9

R103

DD

22

150K

150K

22HDR TP31 TEST

TP85

TP27 TEST

TP25 TEST

150K

C98

R93 182 1% TALIQCOLDSWITCH R113 4.75K

29

ELDRIVE

+70V

+70V

C64 .01UF

100PF

SW1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

DIGITALIC'SBYPASSCAPS

R127 14K 1%

TEST

HDR32

HDR32

C124 .1UF 100V

TP81

TEST

.1UF

R126 390K 1%

BAT_BTN C126

TP86

C97

C95 2.2UF 50V

C113 4.7UF 50V

DISP_PHASE

L12

SI9530

.1UF

CR25 5367A 43V10% 5W

3.32K

1

EX_OUTLSB

VCC U20

10

R96

2

LT1172

JP3 AD9

9

VC GND

3

JP2 O1 O2 O3 O4 O5 O6 O7 O8 O9 O10 O11 O12 O13 O14 O15 O16 O17 O18 O19 O20 O21 O22 O23 O24 O25 O26 O27 O28 O29 O30 O31 O32

SI9530

AD10

8

VCC

CHECK BATTERY

VCC

FB

R125 390K 1%

C92 2.2UF 50V

CR30 MURS110

VIN

6

PWR_DOWN

9 10

C125 22UF

3

GND

VOUT

C82 22UF

7

GND

V+

C110 C67 .1UF

RAW10V

R120 .47UF

5 6

Q1 Q1

74HC74 3.32K

PR_STROBE

5

14

R81

U23

SET1 D1 CLK1 RST1

F2 VBAT

VPRN

C122

C121

C120

100PF

100PF

100PF

TP32 TEST

TP34 TEST TP33 TEST

1A C115 .1UF

32.768KHz

3.32K

HDR7

BT1 3V

Figure 9-36 Auxiliary PCB Schematic Diagram

Nellcor_N-20_Pulse_Oximeter_-_Service_manual.pdf

Recommend Documents