Mallinckrodt Nellcor N-20 Service Manual
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Mallinckrodt Nellcor N-20 Service Manual

Portable pulse oximeter
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Service Manual
N-20/N-20P Portable Pulse Oximeter
Caution: Federal law (U.S.A.) restricts this device to sale by or on the order of a physician.
To contact Mallinckrodt's representative: In the United States, call 1.800.635.5267 or 314.654.2000; outside the United States, call
your local Mallinckrodt representative.
 2000 Mallinckrodt Inc. All rights reserved. 062397B-0600
0123

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Summary of Contents for Mallinckrodt Nellcor N-20

  • Page 1 N-20/N-20P Portable Pulse Oximeter Caution: Federal law (U.S.A.) restricts this device to sale by or on the order of a physician. To contact Mallinckrodt’s representative: In the United States, call 1.800.635.5267 or 314.654.2000; outside the United States, call your local Mallinckrodt representative.
  • Page 2 To obtain information about a warranty, if any, for this product, contact Mallinckrodt's Technical Services Department, or your local Mallinckrodt representative. Purchase of this instrument confers no expressed or implied license under any Mallinckrodt patent to use the instrument with any sensor that is not manufactured or licensed by Mallinckrodt.

  • Page 3: Table Of Contents

    CONTENTS Introduction..............................1-1 Manual Overview ............................1-1 Warnings and Cautions ..........................1-1 Description of N-20 Portable Pulse Oximeter .................... 1-1 Routine Maintenance............................. 2-1 Overview..............................2-1 Cleaning ..............................2-1 Periodic Safety and Functional Checks ...................... 2-1 Battery ................................. 2-1 Performance Verification ..........................3-1 Introduction..............................
  • Page 4 CONTENTS Specifications ..............................8-1 Readout ............................... 8-1 Controls............................... 8-1 Operating Modes............................8-1 Printer Output ............................. 8-2 N-20/N-20P Performance..........................8-2 Sensor Types..............................8-3 Electrical Specifications..........................8-3 Environmental Specifications........................8-4 Physical Specifications..........................8-4 Technical Supplement............................ 9-1 Overview..............................9-1 Functional versus Fractional Saturation ....................9-1 Measured versus Calculated Saturation .....................
  • Page 5 CONTENTS 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 ......................

  • Page 7: Introduction

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

  • Page 9: Routine Maintenance

    The following checks should be performed at least every 2 years by a qualified service technician. Inspect the exterior of the N-20/N-20P for damage. Inspect safety labels for legibility. If the labels are not legible, contact Mallinckrodt Technical Services Department or your local Mallinckrodt representative.

  • Page 11: Performance Verification

    Battery and Pulse Search indicator are lit, the monitor’s backlight is also lit. To test for proper operation of the display backlight, observe the N-20/N-20P in a darkened room. If any backlight section is not working correctly, contact Mallinckrodt's Technical Services Department or Mallinckrodt's local representative for assistance.
  • Page 12 Performance Verification 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...
  • Page 13 Performance Verification • Illuminates the display backlight. 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). •...
  • Page 14 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 either irregular or dots are missing, contact Mallinckrodt's Technical Services Department or Mallinckrodt's local representative for assistance.
  • Page 15 Performance Verification 4. 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.” 5. The OXYGEN SATURATION display momentarily indicates the monitor 3 digit software version.
  • Page 16 Performance Verification 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...

  • Page 17: Troubleshooting

    Obtaining Replacement Parts Mallinckrodt Technical Services provides technical assistance information and replacement parts. To obtain replacement parts, contact Mallinckrodt. Refer to parts by the part names and part numbers listed in Section 6, Spare Parts. Troubleshooting Guide This section discusses potential symptoms, possible causes, and actions for their resolution. Should...
  • Page 18 Troubleshooting contact Mallinckrodt's Technical Services Department or a local Mallinckrodt 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.
  • Page 19 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.

  • Page 20: Service Procedures

    Troubleshooting Cause Action The printer is not operational, but the N-20P continues to Check to see if the paper is jammed. obtain patient measurements. Examine the print head and ensure that it has returned to the home position. Symptom 6: Err followed by a number appears on the display.
  • Page 21 Troubleshooting 4.6.1 Installing Batteries 1. 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. 3. Replace the battery cover access door. 4.6.2 Loading/Clearing Printer Paper The N-20P uses a thermal paper that can show printed characters on one side only.
  • Page 22 Troubleshooting 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. 4.6.4 Replacing the Real-Time Clock (RTC) Battery The socket for the RTC battery (BT1) is located on the auxiliary PCB at grid location 5D.

  • Page 23: Error Codes

    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 Mallinckrodt's Technical Services Department or Mallinckrodt's local representative for assistance.
  • Page 24 Troubleshooting 201–203 Errors in external RAM test 4.7.3 Category 3 — PROM Errors Errors in PROM memory (main PCB). Likely action is replacement of the PROM. Error in PROM test 4.7.4 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.

  • Page 25: Disassembly Guide

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

  • Page 26: Figure 5-1: Sensor Lock, And Printer, Paper, And Battery Access Doors

    Disassembly Guide Figure 5-1: Sensor Lock, and Printer, Paper, and Battery Access Doors 1. Remove the battery door (19) and batteries. 2. Remove the sensor lock (34) by lightly pressing in on its ears and pulling out from the sensor shroud.

  • Page 27: Figure 5-2: N-20 Covers With The Pcb And Display Assembly

    Disassembly Guide 5.2.2 Removing the Covers Figure 5-2: N-20 Covers with the PCB and Display Assembly 1. Remove screw cap (30), and loosen the captive screw (31), which secures the rear cover (15). 2. Separate the front cover (16) from the rear cover by wedging a thin flathead screw driver between the covers at the base of the instrument and slowly prying them apart.

  • Page 28: Figure 5-3: Main, Auxiliary, And Display Pcb Assembly

    Disassembly Guide 5.2.3 Removing the PCBs and Display Assembly Tab #1 Tab #3 Detail B Flex #1 Tab #4 Tab #2 Flex #2 Flex #3 Detail A Figure 5-3: Main, Auxiliary, and Display PCB Assembly 1. Remove the Measure button (6) from the main PCB. 2.

  • Page 29: Figure 5-4: Printer And Flex Circuit Installation

    Disassembly Guide 5.2.5 Disassembling the Printer/Flex Circuit Assembly Figure 5-4: Printer and Flex Circuit Installation 1. Remove the printer button retaining plate (37) by sliding it away from the case assembly. 2. Disconnect the two flex-circuit headers of the printer (29) from the connectors on the printer flex circuit (28) by slowly pulling outward from side to side at alternating ends of the connectors.

  • Page 31: Spare Parts

    SPARE PARTS 6.1 N-20/N-20P Spare Parts N-20/N-20P Spare Parts To order replacement parts, contact Mallinckrodt's Technical Services Department and order by part number. Item numbers correspond to the callout numbers in the figures. Item Designator Description Battery switch (auxiliary PCB)
  • Page 32 Spare Parts Item Designator Description Screw, captive 891324 801025 Screw, Phillips, 4-40 × 1/4 Screw, plastite 871031 Sensor lock 022943 Sensor shroud 022944 Spacer 023452 Stiffener, printer button 023131 023300 Tape, foam (.88" × .38") Transducer, audio, piezo ceramic 691230...

  • Page 33: Packing For Shipment

    Pack the monitor or printer carefully. Failure to follow the instructions in this section may result in loss or damage not covered by the Mallinckrodt warranty. If the original shipping carton is not available, use another suitable carton or call Mallinckrodt Technical Services to obtain a shipping carton.

  • Page 35: Specifications

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

  • Page 36: Printer Output

    Specifications For the N-20, a 2% or greater decrease in SpO 2 is indicated by two brief, low-pitched tones. The N-20P printout shows SpO 2 and pulse rate at 30-second intervals. For the N-20P, a 2% or greater decrease in SpO 2 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.

  • Page 37: Sensor Types

    Specifications Sensor Types Table 8-1: Sensors Sensor Model Patient Size N-25/N-25LF <3 or >40 kg Oxisensor  II oxygen transducers (sterile, single-use only) I-20/I-20LF 3 to 20 kg D-20 10 to 50 kg D-25/D-25L >30 kg R-15 >50 kg OXI-A/N <3 or >40 kg Oxiband ...

  • Page 38: Environmental Specifications

    (7.5 in. × 3.0 in. × 2.5 in.) 8.10 Qualifying Information The Nellcor N-20/N-20P is calibrated to measure arterial hemoglobin oxygen saturation of functional hemoglobin. The specified accuracy of this measurement is based on statistical analysis of arterial blood samples as measured on an IL282 CO-Oximeter.

  • Page 39: Technical Supplement

    9 TECHNICAL SUPPLEMENT 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 SpO Analog Circuit 9.9 Digital Circuitry 9.10 Circuit Illustrations Overview The N-20/N-20P is based on the principles of spectrophotometry and optical plethysmography.

  • Page 40: Circuit Analysis

    Technical Supplement Figure 9-1 illustrates the effect that variations in pH, temperature, partial pressure of carbon dioxide (PCO 2 ), and concentrations of 2,3-DPG and fetal hemoglobin may have on the oxyhemoglobin dissociation curve. Temperature 2,3-DPG Fetal Hb Temperature 2,3-DPG (mmHg) Figure 9-1: Oxyhemoglobin Dissociation Curve Circuit Analysis...

  • Page 41: Spo 2 Analog Circuitry Block Diagram (Figure 9-3)

    Technical Supplement Main PCB Patient sensor analog Microprocessor Memory Display control Sensors: temperature ambient light battery voltage Measure PROM button 20-pin headers Auxiliary PCB Power supply Display Printer interface backlight Flex Display control connectors Audio beeper Batteries 4-6 VDC Check Real- Printer battery...

  • Page 42: Figure 9-4: Digital Circuitry Block Diagram

    Technical Supplement 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 N-20/N-20P Control buttons Check Battery...

  • Page 43: Definition Of Terms

    Technical Supplement 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 Main PCB AUX PCB...

  • Page 44: Overall Block Diagram

    Technical Supplement 9.7.3 Content Addressable Memory (CAM) The CPU controls the HSO lines with the CAM. CAM is software controlled and programmed with events scheduled relative to one of two internal timers. 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.

  • Page 45: Spo 2 Analog Circuitry

    Technical Supplement 9.8.3 Display and Analog Shield Assembly This assembly connects to the main PCB by flex circuits. A metal shield shrouds the SpO analog circuits on the main PCB to protect them from EMI. An integrated electroluminescent backlight illuminates the display under low light conditions. The N-20P has an additional printer control board (printer flex circuit) and printer hardware.
  • Page 46 Technical Supplement If the LEDs reach maximum output without the necessary signal strength, the PWMs will increase the channel gain. The PWM lines will select either a change in the LED current or signal gain, but will not do both simultaneously. The LED circuit switches between red and IR transmission and disables both for a time between transmissions in order to provide a no-transmission reference.
  • Page 47 Technical Supplement Before the current from the photodetector is converted to voltage, any high frequency noise is filtered by C40 and R17. The op-amp U1A is used in parallel with the current-to-voltage converter U1D to cancel any DC voltage, effectively AC coupling the output of U1D. The average value of the SpO analog reference voltage (VREF) of U1D, 5 V, is measured at pin 14 of test point 49.

  • Page 48: Figure 9-11: Variable Gain Circuit

    Technical Supplement VREF C122 .1UF To LED control PWM2 OFF/ON PWM1 IR LED/AV 47.5K .1UF C126 220PF VREF 2N3906 4053 LF444 82.5K TP51 3.32K .47UF C127 220PF VREF VREF 2N3906 82.5K LF444 TP52 Figure 9-11: Variable Gain Circuit 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.

  • Page 49: Figure 9-12: Filtering Circuit

    Technical Supplement REDDC TP81 .12UF 100K .12UF OP490SO 100K 100K OP490SO 100K TP89 VREF .068UF .068UF 1N914 TP82 +12V 1N914 100K 100K .12UF OP490SO .12UF 100K 100K .068UF IRDC OP490SO VREF 1N914 TP90 .068UF 1N914 Figure 9-12: Filtering Circuit 9.9.8 AC Ranging In order to measure a specified level of oxygen saturation and to still use a standard-type combined CPU and A/D converter, the DC offset is subtracted from each signal.

  • Page 50: Digital Circuitry

    Technical Supplement 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—...
  • Page 51 Technical Supplement 9.10.3 Real-Time Clock (RTC) The RTC keeps track of date and time, which is printed on each printout. The RTC is powered by a lithium battery designed to last up to 5 years before needing replacement. 9.10.4 Audio Output A piezoelectric ceramic beeper is used for audio output.

  • Page 52: Figure 9-14: N-20 Hardware Block Diagram

    Technical Supplement Analog Ambient Battery Ambient Reference Light Voltage Temperature Voltage Analog Battery Serial Power Interface C P U Control Power SpO2 Power Patient Analog Analog Control Sensor Control AD Bus Section Power Control Address Address Demultiplexing Decoding Power Supply AD Bus Enables Standard...
  • Page 53 Technical Supplement 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. •...
  • Page 54 Technical Supplement 9.10.9.2 Address Decoding The address decoding circuit is illustrated in Figure 9-16. EXINEN EXOUTEN 20 HDR ADDRESS DECODING TO: N-20 AUX PCB DC00-DFFF 74HC138 U30A E000-FFFF RAMEN 74HC10 TP74 U30B U30C 0000-DBFF ROMEN 74HC10 74HC10 TP71 R134 Figure 9-16: Address Decoding Circuit The CPU has a 64 Kbyte address range of 0-FFFF.
  • Page 55 Technical Supplement 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.
  • Page 56 Technical Supplement 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.
  • Page 57 Technical Supplement 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;...
  • Page 58 Technical Supplement BEEP_1 BEEP_2 TP74 TEST TP75 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.
  • Page 59 Technical Supplement 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.
  • Page 60 Technical Supplement TP72 GO BTN R102 TEST VCON To U21 pin 4 GO_BTN 150K TO: N-20 MAIN PCB 3.32K .01UF JP18 GO_SW TP71 C123 TEST 100PF CHECK BATTERY 150K TP88 TP81 BAT_BTN TEST TEST C126 100PF .01UF TO: N-20 AUX PCB GO_SW MEASURE BUTTON...
  • Page 61 Technical Supplement • 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.
  • Page 62 Technical Supplement and conducts. If batteries are installed backward, Q15 part 2 switches off and disables current flow. This protects the units power supply circuitry from an accidental reversal of battery potential. 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.
  • Page 63 Technical Supplement VREF TP60 R123 R124 RAW10V VOUT TRIM 22UF LT1021 22UF 0.1UF TP70 R161 2N3904 +5.7 2N3904 VREF +12V R121 RAW12V TP61 22UF 0.1UF R122 TP62 RAW-5V 22UF 0.1UF Figure 9-26: Analog Reference Voltage Circuit U32 provides an accurate, regulated voltage that is used as the reference voltage for the A/D inside the CPU.
  • Page 64 Technical Supplement TEMP SENSOR PR_TEMP TEMP 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.
  • Page 65 Technical Supplement 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.
  • Page 66 Technical Supplement SEIKO MTP102-16 PRINTER TO N-20 AUX BOARD VPRN JP10 HEADER 6 DOT4 JP11 OUTM PR_DOT6 DOT6 DOT6 OUT0 DOT5 OUT1 PR_DOT5 DOT4 OUT2 DOT3 OUT3 PR_DOT4 DOT2 OUT4 DOT1 OUT5 PR_DOT3 DOT0 OUT6 PR_DOT2 HEADER 8 PR_DOT1 LB1256 PR_DOT0 PR_MOTOR 3300UF...
  • Page 67 Technical Supplement 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.

  • Page 68: Support Illustrations

    Technical Supplement Constant power (VPRN) and a power control line (PWR_ON) are provided by the auxiliary PCB. Q1 is used as a power control FET. Both halves are used in parallel to reduce the on resistance. When 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;...
  • Page 69 PWM2 SENSOR PWM1 INPUT LED DRIVE VREF .1UF R135 MMBTA56 TP45 3.74K 4.7PF 280K MMBTA56 LT1013 TP83 C116 C117 C118 100K DB9F 100PF 100PF 100PF TP47 TP46 MMBTA06 .1UF 182K .1UF TP50 4053 .022UF C119 VREF TP84 22.1K 100PF TP48 100K .1UF 6.04K...
  • Page 70 TP78 R159 88.7K VREF +12V 2.0K R160 LT1097 51.1K R158 SAMPRED 88.7K SAMPIR OFF/ON LTC201 VREF LF444 390PF TP49 3.32K 82.5K 18PF 3.32K +12V LTC201 .47UF 280K 182K .047UF VREF 3.32K VREF LF444 R157 U6C 10 511K LTC201 .047UF 3.32K LTC201 .47UF TP44...
  • Page 71 OFF/ON (HSO.1) /SAMPIR (HSO.2) /SAMPRED (HSO.0) IR/RED (P1.1) -60µS -60µS µS 105.6 158.4 177.6 283.2 336.0 337.2 443.2 496.0 515.2 620.8 673.6 State Time Figure 9-10 N-20 HSO Timing Diagram 9-35...
  • Page 72 LTC201 LTC201 U11B U11A REDLED/AV From U2 pin 3 IRLED/AV REDDC 3.32K +5.7 .01UF TP54 .01UF 3.32K REDAC 3.32K LMC6044 .1UF .47UF TP55 .015UF 100K U11C .01UF LTC201 34.8K 3.32K VREF PWM1 12.1K TP56 LMC6044 TP85 47.5K .1UF TP57 4053 REDLED/AV PWM0 100K...
  • Page 73 EX_OUT LSB DISP_DATA DISP_CLK RTC_CLK RTC_RST PR_MOTOR PR_MEAS BEEP_1 BEEP_2 EXOUTEN R132 74HC574 150K TP82 TEST EX_OUT MSB PR_DOT6 PR_DOT5 AD10 PR_DOT4 AD11 PR_DOT3 AD12 PR_DOT2 AD13 PR_DOT1 AD14 PR_DOT0 AD15 RTC_IO EXOUTEN PR_STROBE R148 74HC574 R149 R123 150K 150K R150 150K R151...
  • Page 74 DISP_POL DISPLAY DRIVERS DISP_DL VDISP TP80 TEST DISP_DATA +70V DISP_PHASE DISP_CLK LATCH +70V TALIQ COLD SWITCH DOUT R113 4.75K MMBT5401L VDISP R116 390PF OSCIN MMBT5551L R115 OSCOUT 390PF R117 2N3904 6.19K 475K R114 MMBT5551L 12.1K HDR 32 SI9530 LATCH DOUT DISPLAY PS CTRL SET1 DISP_POL...
  • Page 75 BATTERY INPUT BATT GND TO CENTER MOUNTING HOLE TEST R155 POWER SUPPLY VBAT BATT PLUS TEST 1.5A R134 C116 C117 ILIM 22UF 22UF 22UF CR24 100PF 0.1UF 100K GATE TRANZORB 120UH 100K SI9405DY 22UF .1UF SI9956DY CR13 LT1173 C118 C119 31.6K 130T3 RAW-5V...
  • Page 76 VCON LT1046 CR11 TP84 VBAT TEST 1N914 TP72 R102 0.1UF TEST VCON VCON SET1 GO_BTN PWR_ON 150K TO: N-20 CLK1 RST1 MAIN PCB TP83 3.32K TEST SET2 VCON .01UF JP18 GO BTN CLK2 GO_SW RST2 R110 475K TP71 C123 TEST 74HC74 3.32K C110...
  • Page 77 ON BTN DD BTN ADV BTN PR_PRESENT VPRN R143 U36B PR_HEAD1 14.0K LT1017CS TP78 TEST VPRN R144 R146 1.24K TP79 U36A PR_HEAD2 TEST LT1017CS R145 60.4K VPRN TP77 TEST R106 R142 TO PRINTER PCB 150K 2N3904 TP35 TP36 TP37 150K TEST TEST TEST...
  • Page 78 SAMPIR SAMPRED PWM1 AC + DC Input Signal Conditioning Signal Gain AC Ranging /ZERO PWM0 REDAC Variable Gain Offset Variable Gain Zeroing and Filter Subtraction and Filter PWM2 DMUX PWM0 Current to Voltage Variable Gain Offset Variable Gain IRAC Conversion and Filter Subtraction and Filter...
  • Page 79 VREF PR_HEAD1 VREF T2CLK/P2.3 PR_HEAD2 ANGND T2RST/P2.4 REDDC REDLED/AV ACH0/P0.0 P2.6/T2U-D REDAC /ZERO ACH1/P0.1 P2.7/T2CAPT IRDC PHOTOI ACH2/P0.2 HSI0 IRAC ACH3/P0.3 HSI1 RSENS DISP_PHASE ACH4/P0.4 HSI2/HSO4 R137 AMB_LIGHT PR_STROBE ACH5/P0.5 HSI3/HSO5 BAT_VOLT SAMPRED ACH6/P0.6 HSO0 PR_TEMP OFF/ON ACH7/P0.7 HSO1 PR_TACH SAMPIR EXTINT/P2.2 HSO2...
  • Page 80 LIGHT SENSOR TO: N-20 SpO2 ANALOG DIGITAL SECTION AUX PCB VTB8442B GO_SW TP78 MMBTA13L TP72 +12V +12V R159 2.2M PR_HEAD1 GO BUTTON R136 88.7K VREF +12V C124 C125 +12V 33.2K PR_HEAD2 .01UF .1UF .1UF VREF PR_STROBE TANT C122 LTC201 LTC201 2.0K ACROSS U35 22UF...
  • Page 81 BATTERY INPUT BATT GND TO CENTER MOUNTING HOLE TEST R155 POWER SUPPLY VBAT BATT PLUS TEST 1.5A R134 C116 C117 ILIM 22UF 22UF 22UF CR24 .1UF 100K CR27 GATE TRANZORB 1N914 120UH SI9405DY 100K 100PF 22UF R100 SI9956DY .1UF VRECHARGE LT1173 TEST R101...
  • Page 82 TO N-20 POWER SUPPLY BOARD VPRN JP10 SEIKO HEADER 6 DOT4 MTP102-16 JP11 PRINTER OUTM PR_DOT6 DOT6 DOT6 OUT0 DOT5 OUT1 PR_DOT5 DOT4 OUT2 DOT3 OUT3 PR_DOT4 DOT2 OUT4 DOT1 OUT5 PR_DOT3 DOT0 OUT6 PR_DOT2 HEADER 8 PR_DOT1 LB1256 PR_DOT0 PR_MOTOR 3300UF ON OFF BUTTON...

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