Novametrix 615 Service manual
HAND-HELD
CAPNOGRAPHY
Service Manual
Model 615
Mar 23, 2000
Catalog No. 9425-90-00
Novametrix Medical Systems Inc.
5 Technology Drive
Wallingford, Connecticut, U.S.A. 06492.
About This Manual
About This Manual
Revision Histor
Declaration of Conformity with European Union Directives
This manual is intended for use by technical personnel for servicing the Model 615. Refer to the
Model 615 User’s Manual (Cat. No. 9425-23) for detailed information on normal operation.
®
TIDAL WAVE and CAPNOSTA
Inc. Nafion is a registered trademark of Dow Corning Corp. The Model 615 is Year 2000
compliant.
Copyright 2000 Novametrix Medical Systems Inc. This document contains information which
is proprietary and the property of Novametrix Medical Systems Inc., and may not be
reproduced, stored in a retrieval system, translated, transcribed or transmitted in any form, or by
any means, without prior explicit written permission from Novametrix Medical Systems Inc.
23-Mar-00 Release, revision 00
are registered trademarks. Cidex is a trademark of Arbook,
The authorized representative for Novametrix Equipment is:
European Compliance Services Limited
Oakdene House
Oak Road
Watchfield
Swindon, Wilts SN6 8TD
UK
Manufacturing, Quality and Safety
Novametrix manufacturing facility is certified to ISO 9001 and EN46001 (MDD93/42/EE
Annex II). Novametrix Medical Systems Inc. products bear the “CE 0086” mark. The product
is certified by Underwriter’s Laboratories (UL) to bear the UL mark; and tested by TUV
Rheinland to IEC601-1 / EN60601-1.
Rev. 00
Model 615 Service Manual
iii
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Manufacturing, Quality and Safety
iv
Model 615 Service Manual
Rev. 00
Contents
General Description .....................................................................................................1
Indication for use .........................................................................................................1
Keypanel Controls and Indicators ...............................................................................1
Connections and Labeling ...........................................................................................3
Principle of operation ..................................................................................................3
Safety .............................................................................................................................4
Theory of Operation .....................................................................................................7
Digital Control System .................................................................................................7
Background Mode Debugging .........................................................................11
System Memory ...............................................................................................11
Serial Communications ....................................................................................12
User Interface Control Circuitry .......................................................................12
Real Time Clock, Power on RESET Generation and Glue Logic .................... 13
CO2 System Analog Subsections .............................................................................13
CO
Source Drive ............................................................................................13
2
CAPNOSTAT® CO2 sensor Case and Detector Heater Control ....................15
CO
Input Signal Path .....................................................................................16
2
CAPNOSTAT® CO2 sensor Interface .............................................................16
Barometric Pressure Circuitry ..........................................................................16
Sampling Pump ...............................................................................................17
Digital and Analog Control Lines .....................................................................17
Power Supply and Battery Charger ...........................................................................18
Supply and Reference Voltage Generation .....................................................18
Battery Charger Circuitry .................................................................................20
Functional Tests .........................................................................................................23
Equipment Required .................................................................................................23
Procedure ..................................................................................................................23
Power up .........................................................................................................23
Capnography Tests .........................................................................................24
Sidestream Tests .............................................................................................25
Miscellaneous Tests ........................................................................................25
Accuracy Tests ...........................................................................................................27
Equipment Required .................................................................................................27
Procedure ..................................................................................................................27
Electronic Tests ..........................................................................................................31
Equipment Required .................................................................................................31
Test Procedure ..........................................................................................................31
Safety Testing ...........................................................................................................34
Status Messages ........................................................................................................35
System Messages .....................................................................................................35
Capnography Messages ...........................................................................................35
Maintenance ................................................................................................................37
General ....................................................................................................................37
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Model 615 Sevice Manual
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Contents
Maintenance Schedules ............................................................................................37
Cleaning and Sterilization ......................................................................................... 38
Monitor, BaseStation and External Power Supply .......................................... 38
CAPNOSTAT® CO
Single Patient Use Airway Adapters ............................................................... 38
External Sampling System Components ......................................................... 38
Internal Sampling System Components .......................................................... 38
Battery Maintenance .................................................................................................39
AC/Battery Operation ...................................................................................... 39
Battery Status and Alerts ................................................................................ 40
Removing and Installing the Battery ............................................................... 41
Charge using External Power Supply ............................................................. 41
Charge using optional BaseStation ................................................................. 42
Charging with External Charger ...................................................................... 42
AA Lithium Batteries ........................................................................................ 43
Battery Life and Recharge Times .................................................................... 44
Assembly Exchanges ................................................................................................ 44
Disassembling the Monitor .............................................................................. 44
Reassembling the monitor .............................................................................. 47
Serial Communications/Power Interface Connector ................................................. 47
Software Update Instructions .................................................................................... 48
Equipment Required ....................................................................................... 48
Setup ...............................................................................................................48
Procedure ........................................................................................................ 48
Specifications ............................................................................................................. 53
Specifications ............................................................................................................ 53
General ........................................................................................................... 53
Capnograph .................................................................................................... 53
EtCO2 Section (Mainstream) ..........................................................................53
Respiratory Rate (Mainstream) ....................................................................... 53
EtCO2 Section (Sidestream) ........................................................................... 54
Respiratory Rate (Sidestream) ........................................................................ 54
Monitor Specifications ............................................................................................... 54
Additional Features ......................................................................................... 55
Accessories ................................................................................................................ 57
Sensor ........................................................................... 38
2
vi
Model 615 Service Manual
Rev. 00
General Description
Power key
Page key
Backlight key
Battery charge indicator
Alert key
Adapter key
AC indicator
Display screen
and LED
Alert LED
Section 1
Section 1
1.1 Indication for use
The Model 615 hand-held, portable Capnograph is intended to be used for monitoring end tidal
CO
and respiration rate in monitoring environments such as ventilatory support, emergency
2
and anesthesia. The Model 615 incorporates a miniature vacuum pump to draw expired
respiratory gases through the CAPNOSTAT
nasal cannula. The Model 615 is designed to monitor adult, pediatric and neonatal patients and
is not intended for any other purpose.
Components of this product and its associated accessories which have patient contact are
free of latex.
1.2 Keypanel Controls and Indicators
General Description
®
CO2 Sensor using a sampling airway adapter and
NOTE
Rev. 00 Model 615 Service Manua
Switches power on/off.
Displays, Capnogram, EtCO
enter the PRINT SELECTION menu.
Sets 2 minute silence and displays the SET ALERTS menu. Press and hold for
3 seconds to disable audible alerts. Press and hold again to cancel.
The Alert Key LED:
Steady yellow: audio silenced for 2 min., no alert in progress.
Flashing yellow: audio off , no alert in progress.
Flashing red and yellow: alert in progress; audio is off or
trend or respiration rate trend. Press and hold to
2
2 minute silence.
1
Section 1
General Description
Press to set adapter type. Press and hold for 4 seconds to zero adapter.
Press to turn backlight on/off, or press and hold to adjust contrast.
INDICATORS
Illuminates when on battery power. Green; battery is fully charged, slow flashing yellow; battery power is low (approximately 20 minutes of operation), Fast
flashing red; battery is exhausted (approximately 5 minutes of operation).
Green when the monitor is connected to an AC power source.
ICONS
Audible alerts permanently silenced.
Audible alert silenced for two minutes.
Alert limits disabled.
Indicates adapter key.
Time/Date Icon
Indicates backlight key.
Displayed beside any Trend screen.
Displayed when performing an adapter zero and the sensor is not at operating
temperature.
Displayed when performing an adapter zero and breaths are detected.
®
Displayed when CAPNOSTAT
are detected.
CO2 sensor is attached to patient and breaths
SYMBOLS
Patient isolation: Identifies connection as type BF
Attention: Consult manual for detailed information
Model 615 Service Manual Rev. 00
2
General Description
Sa mpling sy ste m inpu t
Sam pling system output
Endview
Model 615
Rearview
Model 615
RS232 connection
DC input
Battery c om pa rtme nt
Sideview
Model 615
and external power
input from BaseStation
1.3 Connections and Labelin
Section 1
Sampling System: Gas output
Sampling System: Gas input
DC input. Connect external power supply to this port. Use only Novametrix
external power supply, Catalog number 9220-10.
Recyclable item. This symbol is found on the internal battery and should not
concern the common user. Refer to qualified service personnel when battery
replacement is required.
1.4 Principle of operation
The Model 615 uses the CAPNOSTAT® CO2 sensor to measure CO2 by using the infrared
absorbtion technique, which has endured and evolved in the clinical setting for over two
decades and remains the most popular and versatile technique today.
The principle is based on the fact that CO
specific wavelengths, with the amount of energy absorbed being directly related to the CO
concentration. When an IR beam is passed through a gas sample containing CO2, the
electronic signal from the photodetector (which measures the remaining light energy) can be
obtained. This signal is then compared to the energy of the IR source and calibrated to
accurately reflect C
concentration in the sample. To calibrate, the photodetector’s response
2
to a known concentration of CO
channel accounts for optical changes in the sensor, allowing the system to remain in calibration
without user intervention.
Rev. 00 Model 615 Service Manua
is stored at the factory in the monitor’s memory. A reference
2
molecules absorb infrared (IR) light energy of
2
2
3
Section 2
Safety
Section 2
For maximum patient and operator safety, you must follow the following warnings and cautions.
Indicates a potentially harmful condition that can lead to personal injury.
•
Explosion Hazard:
of this instrument in such an environment may present an explosion hazard.
•
Electrical Shock Hazard:
before cleaning it. Refer servicing to qualified service personnel.
•
Failure of Operation:
situation has been corrected by qualified personnel.
• Do not operate Model 615 if it appears to have been dropped or damaged.
• Do not operate Model 615 or its accessories when it is wet due to spills or condensation.
• Never sterilize or immerse the monitor, sensor or accessories in liquids.
• The monitor does not alert for NO RESPIRATION if the airway adapter is removed from the
CAPNOSTAT
• Verify the “No Resp Timer” setting prior to use.
• Do not position any sensor cable in a way that may cause entanglement or strangulation.
• The Model 615 is not intended to be used as a primary diagnostic apnea monitor and/or
recording device.
• The external battery charger should NOT be used to recharge the battery near or in close
proximity to patients and/or other medical equipment in operation. It is intended for use in
service areas only (i.e. nurses station, biomed lab, etc.).
• Connection of an external device (e.g. printer or computer) to the RS232 serial port on the
BaseStation may compromise patient safety.
DO NOT
If the monitor fails to respond as described, do not use it until the
®
CO2 sensor.
Safety
WARNINGS
use Model 615 in the presence of flammable anesthetics. Use
Always turn Model 615 off and remove any external devices
CAUTIONS
Indicates a condition that may lead to equipment damage or malfunction.
• Federal (U.S.A.) law restricts this device to sale, distribution, or use by or on the order of a
licensed medical practitioner.
• Use only an external power supply approved by Novametrix for use with this device. Use
of any other power supply may damage the Model 615 and void the warranty.
• Do not operate Model 615 or its accessories when it is wet due to spills or condensation.
• Do not operate Model 615 if it appears to have been dropped or damaged.
• Keep Model 615 and its accessories clean.
• Inspect the integrity of the Model 615 and its accessories prior to use.
• Never sterilize or immerse the monitor, sensor or accessories in liquids.
• Do not sterilize or immerse sensors except as directed in this manual.
• Do not apply excessive tension to any sensor cable or pneumatic tubing.
• Do not store the monitor or sensors at temperatures less than 14°F (-10°C) or above 131°F
(55°C).
• Do not operate the monitor or sensors at temperatures below 50°F (10°C) or above 104°F
(40°C).
Model 615 Service Manual Rev. 00
4
Safety
Section 2
• If a Single Patient Use Sampling Adapter becomes occluded, replace and discard the
adapter.
• It is recommended that the CAPNOSTAT
®
CO2 sensor be removed from the circuit
whenever an aerosolized medication is delivered. This is due to the increased viscosity of
the medications which may contaminate the sensor windows, causing the sensor to fail
prematurely.
• Where electromagnetic devices (i.e. electrocautery) are used, patient monitoring may be
interrupted due to electromagnetic interference. Electromagnetic fields up to 3V/m will not
adversely affect system performance.
• Refer servicing to qualified personnel.
NOTES
Indicates points of particular interest or emphasis for more efficient or convenient operation.
• The Model 615
monitor is intended for operation with Novametrix Single Patient Use airway
adapters.
• Operating the Model 615
below 50°F (10°C) will result in longer warm-up time and reduce
battery life.
• Components of this product and its associated accessories which have patient contact are
free of latex.
• Certain rebreathing circuits, or the presence of artifacts such as cardiogenic oscillations,
may cause Model 615 to react to non-respiratory CO
fluctuations as if they were breaths.
2
This condition affects only the RESP numerical displays; the capnogram display continues
to provide an accurate picture of the CO
waveform.
2
• After the life cycle of our equipment and all accessories has been met, disposal of the
equipment should be accomplished following the national requirements. Contact the local
Novametrix representative for questions concerning disposal.
Rev. 00 Model 615 Service Manua
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Section 2
Safety
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Model 615 Service Manual Rev. 00
6
Section 3
The Model 615 is a microprocessor based handheld instrument that measures the clinica
parameters of CO
the Model 615 is explained in detail in the subsections that follow.
3.1 Digital Control System
Refer to 2754-03 schematic sheet 1.
Embedded control for the system is provided by IC1, a Motorola MC68332 integrated
microcontroller. In addition to a full 32-bit Central Processing Unit (CPU), this device also
contains circuitry for system clock generation, peripheral chip select generation, data control,
interrupt generation, a sophisticated timing coprocessor, synchronous serial communication
and asynchronous serial communication. In general, functional signals are grouped together
into ports, and each signal can be independently programmed by software to be its predefined
port function or as discrete I/O. Additionally, the functionality for several ports (Port C, E and F)
can be predefined by the state of the data bus on system power-up. A special “background
mode” port allows the device to be controlled by an external source for system debugging and
testing. Also integrated on-chip are several activity monitors, as well as a software watchdog to
ensure proper device and system operation. Refer to table 1.
production and respiration rate (RR). The electronic theory of operation of
2
Theory of Operation
Table 1: CPU Port Functions
Functionality Control ,
Port Defined Function
TPU
16 Channels
QSM
4 Synchronous Serial
Chip Selects & one
asynchronous serial
channel
Background Mode System debugging Allows an appropriate external
Timing Signal Generation Each channel independently user
programmable as TPU function or
as Discrete I/O
Serial Communications Port:
QSPI: Queued Serial Peripheral
Interface
SCI: Serial Communications
Interface
QSPI chip selects independently
user programmable, can be used as
Discrete I/O or decoded to create up
to 16 chip selects. SCI transmit can
be programmed as Discrete I/O
device to control the microprocessor
and system
Data Bus Control
(Alt Functions: D pulled low)
Rev. 00 Model 615 Service Manua
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Section 3
Theory of Operation
Table 1: CPU Port Functions
C Chip Selects D0: CSBOOT* data width, 8 or 16-
bit
D1: CS1*-CS3* or
BR*,BG*,BGACK*
D2: CS3*-CS5* or FC0-FC2
D3-D7: CS6*-CS10* or A19-A23
E Bus Control D8: Control Signals or discrete I/O
F MODCK and Interrupts D9: MODCK & IRQ or discrete I/O
The maximum operating frequency of the integrated processor is 20.97 MHz. The operating
frequency is software selectable and generated by an internal VCO operating from Y1, a
32.768KHz watch crystal. The Timing Processor Unit (TPU) coprocessor of the MC68332
provides timing generation derived from the system clock. This feature is utilized to control the
precise timing required for the acquisition of the end tidal carbon dioxide (EtCO
) signals. The
2
TPU is also use to generate the PWM (Pulse Width Modulation) control for the CAPNOSTAT
CO2 sensor case and detector heaters, as well as to provide the frequency generation for the
audio tones. See Tables 2 & 3.
®
Table 2: TPU Timing Generation for the EtCO
subsystem
2
Signal Name Description Function / Timing
CO2AZ Auto Zero Clears the sample/hold circuitry
prior to data acquisition.
Active high, 2.84 ms
CO2PWENB Pulse Width Enable Defines the active time for both
phases of the bipolar source
pulse, used for pulse width protection circuitry.
Active high, 830 µs
SRCDRV0 Source Drive 0 First source drive signal.
Active high, 405 µs
CS*/H Current Sample/Hold Enables circuitry for source cur-
rent measurement. Sample is
taken when SRCDRV0 is
active.
Low = sample, 270 µs, High =
hold
SRCDRV1 Source Drive 1 Second source drive signal
delayed for 30 microseconds
after SRCDRV0 ends.
Active high, 395 µs
Model 615 Service Manual Rev. 00
8
Theory of Operation
Section 3
Table 2: TPU Timing Generation for the EtCO
SS*/H Signal Sample/Hold Enables circuitry for CO
subsystem
2
and
2
reference channel data acquisition.
Low = sample, 270 µs, High =
hold
CASEPWM Case Heater PWM PWM control for the case
heater servo
DETPWM Detector Heater PWM PWM control for the detector
heater servo
TONE Audio Tone Generation Variable frequency outputs to
generate system audio
CASEOT Case Heater Over Temperature Case heater over temperature
shut down
DETOT Detector Heater Over Temperature Detector heater over tempera-
ture shut down
Ferrite and L-C filters, 100pF capacitors, and 100 ohm resistors have been placed on selected
microprocessor signals with fast rise and fall times (including timing, clock, and address and
data lines) in order to help reduce and suppress the radiation of electromagnetic interference
and decouple unwanted power supply noise. In addition, good EMI/EMC design techniques
have been incorporated in the component layout and printed circuit board layout and
manufacture.
Table 4 lists the chip select, control and discrete I/O functions for the
Model 615
system module.
On power-up, Ports E and F are programmed as discrete inputs by pulling down their controlling
data lines, DB8 and DB9. After power-up, the software sets up each pin function individually
and performs a series of self tests to check the integrity of the system. The state of configuration
inputs on Port E (TST*, CNFG0*, CNFG1*, and CNFG2) are read. These inputs allow the
software to identify different operating states such as Test Mode, or different hardware
configurations. After the initialization period is complete and all system functions have been set,
Rev. 00 Model 615 Service Manua
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Section 3
Theory of Operation
the LED output (PF0) toggles at a 1Hz rate switching transistor Q3 which drives the status LED
D3, indicating that the system is ready for operation.
Table 3: Chip Select, Control and Discrete I/O
Port Pin Functions System Signal Name I/O Comments
C D0 pulled low, D1-D7 pulled high, pins are chip select on power-up
CSBOOT* ROMOE* O Program PROM chip select
byte wide mode, (8-bits) D0 =
LOW
CS0* / PC0 / BR* SRAMWR* O SRAM write enable
CS1*/ PC1 / BG* AUD_CS* O Audio attenuation control chip
select
CS2* / PC2 /
BGACK*
CS3* / PC3 / FC0 ROMWR* O FLASH PROM Write Enable,
CS4* / PC4 / FC1 DISPCS1* O LCD chip select #1
CS5* / PC5 / FC2 DISPCS2* O LCD chip select #2
CS6* / PC6 / A19 LATCH1_CS* O System control signals latch 1
CS7* / PC7 / A20 LATCH2_CS* O System control signals latch 2
CS8* / PC8 / A21 ROMWREN O Port C discrete output, prevents
CS9* / PC9 / A22 PROFILE* O Enables software profiling data
CS10* / ECLK /
A23
SRAMRD* O SRAM read enable, byte mode
Byte Mode
chip select
chip select
unintentional writes to FLASH
EPROM. This signal must be
asserted before ROMWR* in
order to overwrite the flash.
output latch
ECLK O Enable clock for the liquid crystal
display
Model 615 Service Manual Rev. 00
10
Theory of Operation
Section 3
Table 3: Chip Select, Control and Discrete I/O
E D8 pulled low, discrete I/O on power-up
DSACK0* / Port E0TST* I Initiate system TEST if low
DSACK1* / Port E1DS1* I Data and size acknowledge 1*
AVC* / Port E2CNFG0* I Configuration switch 0
RMC* / Port E3CNFG1* I Configuration switch 1
DS* / Port E4DS* O Data strobe
AS* / Port E5 AS* O Address strobe
SIZ0* / Port E6 CNFG2* I Configuration switch 2
SIZ1* / Port E7 SLP* I Not used in Model 615
R/W* WR* O Data write strobe
F D9 pulled low, discrete I/O on power-up
MODCK / Port F0 LED O LED CPU activity Indicator
IRQ1* / Port F1 SW1 I Keypanel switch 1 input
IRQ2* / Port F2 SW2 I Keypanel switch 2 input
IRQ3* / Port F3 SW3 I Keypanel switch 3 input
IRQ4* / Port F4 SW4 I Keypanel switch 4 input
IRQ5* / Port F5 PWRKEY I Power key status input
IRQ6* / Port F6 EXTDCIN I Indicates external AC mains
power operation
IRQ7* / Port F7 NMI I Non-maskable interrupt
Background Mode Debugging
External system debugging is possible by connecting an appropriate device (emulator or
debugger) to header J401 and momentarily bring the BERR* (J401/2) low. This halts the bus
activity and turns control of the system over to the external device. In this mode, internal MPU
registers can be viewed and altered, special test features can be invoked and system memory
can be read and written to.
System Memory
An 8-bit wide data path is used for FLASH PROM and SRAM transfers. Program code storage
is contained in a 1-Meg 5V FLASH or EEPROM (IC2) device. The FLASH PROM is protected
from unintentional overwrites of the program code by transistor Q1 and the ROMWREN signal.
Rev. 00 Model 615 Service Manua
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Section 3
Theory of Operation
The ROMWREN line must be high prior to writing new code into the FLASH devices.
Nonvolatile data storage is contained in the 1-Meg SRAM (IC3). The SRAM is backed-up to
retain it’s contents by applying a voltage on VBACKUP generated by BT1 (a 3.0V lithium
battery) when power is off or the battery is removed from the monitor. During the battery backup
state, transistor Q2 keeps the CS1* control of the SRAM in the inactive state. This forces the
data bus to a high impedance state, isolating the SRAM from the rest of the system. True
nonvolatile storage for the bootstrap parameters for the CAPNOSTAT
®
CO2 sensor are stored
in a serial EEPROM (IC2) located on the Interface (2753) board.
Serial Communications
Refer to 2754-03 schematic sheet 6.
The on-chip (IC1) asynchronous serial communications interface (SCI) channel is contained in
the MC68332. The signals are level shifted to standard RS232 levels by IC26 which is a Dual
RS232 Communications Driver/Receiver. The transmitters in the RS232 level shifter are under
software control to minimize the patient leakage current to the rear panel connector (J101
when communication is not active. The signal COMMPWR controls the transmitters operation
and is derived from IC9 pin 14 (schematic sheet 2). The serial connection to external, nonpatient contact devices is electrically isolated from the patient through the CAPNOSTAT
sensor airway adapter. This connector, J101 is located on the rear panel and is designed to
interface with external devices (i.e. computer, printer) when placed in a base station which
contains the mating connector. In addition there is a 4 pin connector (J403) available for test
and service which offers an internal connection to the serial communications at a TTL level. The
data signals ASRxD and ASTxD are logic level signals and are diode protected against over
voltage by D22 and D23 should IC26 breakdown from ESD (schematic page 6). Refer to Table
5 for the pinout and signals of serial interface connector J101.
®
CO
2
Table 4: Power/Communications 6-pin modular connector J101 located on the rear panel.
Pin Number Signal Function
1 RxD Internal MC68332 UART Receive, RS232 Signal, Level
Shifted
2 TxD Internal MC68332 UART Transmit, RS232 Signal, Level
Shifted
3 DGND Digital Ground
4 DGND Digital Ground
5
6 +VCHG External DC input supply to power unit and battery charger
User Interface Control Circuitry
Refer to 2754-03 schematic sheet 2.
The user interface features a 64 row by 128 column Liquid Crystal Display (LCD) module with
an LED backlight. A 5-switch membrane keypanel is provided for operator entry. The use
interface also contains three LED’s which represent various system conditions.
Control of the user interface is provided by the LATCH1_CS* chip select signal together with
the Port F input signals from the microprocessor. SW1-SW4 are inputs which read in the
Model 615 Service Manual Rev. 00
12
Theory of Operation
Section 3
present state of the membrane keys. Depressing a key causes the signal line to be pulled low
in contrast to its normally high state. IC9 provides a latched output for controlling the status
LED’s. The LCD backlight is a series of LED’s which are driven by a 5.12kHz clock signal in
order to lower the LCD backlight power requirement and is activated by the backlight
membrane key. The LITE_CLK signal is a 5.12kHz logic level signal generated by IC7 (sheet
7) which modulates the LED backlight through FET switch Q4 (BKLGHT_OUT) when asserted
by IC10 (BACKLIGHT). This signal is capacitively coupled by C42 in order to prevent the
backlight from remaining on in the event of a system failure.
Contrast control for the LCD is provided by DAC IC33 (sheet 6) and amplifier IC34A and
transistor Q18 (schematic sheet 6). When the CPU detects a press and hold of the backlight
membrane key, the CPU sends a digital ramp input to the DAC which causes the output to
change accordingly. Inverting amplifier IC34A controls the base current into transistor Q18,
which changes the level of the display contrast voltage, VDISP.
Refer to schematic sheet 6.
An audio frequency tone is generated by the TPU (Time Processor Unit) of the MC68332
(TONE). This signal is fed into the divider network consisting of R183 and IC32. IC32 is a 10k
2
ohm E
for attenuating the signal under CPU control. From the divider output the signal is amplified by
IC34B and Q17 which drives the system speaker (LS1) to produce system audio. The AUD_EN
line from IC9 controls Q19, when high the input to IC34B is grounded thus muting the audio.
potentiometer whose value (when written to under software control) provides a means
Real Time Clock, Power on RESET Generation and Glue Logic
Refer to 2754-03 schematic sheets 1 and 2.
Time-keeping for date and time stamping of patient trend information is provided by IC8. This
device contains a built-in crystal for precise time and date measurement. In the absence of
digital power, the time keeping function is maintained by the battery backed supply, VBACKUP
which is generated by the 3V lithium backup battery (BT1).
On power-up, the system is forced into a “Reset” state by IC4 (sheet 1). When the suppl
voltage VDD, approaches 1V, the SRST* line is asserted to prevent undefined operation. IC4
also provides supervision over the VDD logic supply. If the logic supply falls below 4.55V
±120mV then IC4 generates a reset condition until the supply returns to a safe level. Inverter
IC5 is used to generate the active high RESET signal.
The
Model 615
the glue logic required is a minimum. Chip selection for the serial peripherals is provided by
decoding the queued serial module (QSM) (PCS0-PCS3) of the microprocessor IC1 (sheet 1
on schematic) using decoder IC12 (sheet 2) while parallel interface peripherals are selected by
the internal chip select registers of Port C (BOOTCS* and CS0*:CS10*). Latch IC10 is used to
control the saturation analog signal processing, the LCD backlight, the sidestream sampling
pump, and to power the monitor off.
makes use of the high level of integration offered by the MC68332. Therefore
3.2 CO2 System Analog Subsections
CO2 Source Drive
Refer to 2754-03 schematic page 3 and Table 2 of this document.
The source drive circuitry is designed to drive the source with a bipolar signal to prevent the
migration of charges within the source that may result from unidirectional electrical fields. The
Rev. 00 Model 615 Service Manua
13
Section 3
Theory of Operation
resistance of the source is monitored constantly to ensure the integrity of the system by
sampling the current through the source while it is active.
The SRCDRV0 and SRCDRV1 lines are used to control the bipolar signal that drives the
source. The SRCDRV0 signal goes high as soon as the CO2AZ (Auto Zero) line goes low and
the CO2PWENB (Pulse Width Enable) line goes high. The duration of SRCDRV0 is 405 us
(microseconds), and drives the source in the positive direction. The SRCDRV1 line drives the
source with an opposite polarity signal when high for the same duration. There is a 30 us delay
from the time the SRCDRV0 line goes low to when the SCRDRV1 line goes high. This delay is
to prevent the possibility of both SRCDRV0 and SRCDRV1 being active at the same time, thus
creating a low impedance path between the two supplies (power supply shoot-through).
SRCDRV1 steers current through the source in an opposite direction from SRCDRV0.
When SRCDRV0 and CO2INH (Inhibit) are high, the output of MOSFET Driver IC13A pin 7 will
go low. This turns the P-Channel half of MOSFET Q5 on. At the same time, the output of
MOSFET Driver IC14B pin 6 will be high biasing on the N-Channel half of MOSFET Q6 on. With
both Q5B P-Channel and Q6A N-Channel on, current will flow from +VSRC through Q5B to the
positive source terminal, then back from the source negative terminal through Q6A, through
R97 to -VSRC. When SRCDRV0 returns low, both Q5B and Q6A are turned off and no current
flows through the source. After the 30 us delay, SRCDRV1 will go high. The output of IC14A pin
8 will go high, biasing the N-Channel section of MOSFET Q5 on. The output of IC13B pin 5 will
go low, turning the P-Channel of Q6 on. Current will now flow from +VSRC through Q6B to the
source negative terminal, back from the source positive terminal through Q5A and R97 to VSRC. Current will cease to flow when SRCDRV1 goes low. The bridge circuit of Q5 and Q6 in
effect switches the polarity of the drive signal of the source between +VSRC and -VSRC.
CO2PWENB also falls with the falling edge of SCRDRV1, signaling the end of source activity.
When current flows through the source, it will also flow through current sensing resistor R97,
creating a differential voltage proportional to the source current:
V
= (VSR / RSR) * RS * A
SRC
V
=voltage out of difference amplifier proportional to current
SRC
V(DA)
where:
through the source element = 24V +/- 0.625V
V
=differential voltage across the source element
SR
R
=resistance of the source element
SR
=resistance of the current sensing resistor = 1 ohm
R
S
=difference amplifier gain = 5
A
V(DA)
V
=[120 (Volts*Ohms) / SR]
SRC
The voltage signal out of difference amplifier IC15B is level shifted through C52 and fed to the
sample and hold IC16A via buffer amplifier IC15A. A low level on the CS*/H (Current Sample
and Hold) signal allows the source current signal to be sampled. On the rising edge of CS*/H,
the present voltage level of the source current signal is held and appears at the input to channel
A2 of the Analog to Digital Converter IC6 (sheet 2 on schematic) for processing by the MPU.
When CO2AZ is high, the input to the sample and hold of IC16A is grounded to discharge any
residual charge that may be on C52.
In order to prevent the source from being driven until the system is up and ready, there i
protection circuitry that inhibits the source drive until enabled. During system power-up, the
RESET line keeps Q7 on. This causes the CO2INH line to be brought low, preventing source
pulses by pulling down SRCDRV0 and SCRDRV1 through D6. Protection circuitry also guards
against extended pulse width as well as shortened duty cycle. On the rising edge of
CO2PWENB, the trip point of IC17B is exceeded, allowing C55 to charge through R100. If the
Model 615 Service Manual Rev. 00
14
Theory of Operation
CAPNOSTAT® CO2 sensor Case and Detector Heater Control
Section 3
SRCDRV signals do not turn the Source Pulse off within 200 us after the 830 us pulse period,
the trip point for IC17A will be exceeded, pulling the CO2INH line low turning the Pulse off.
After the CO2PWENB signal returns low, capacitor C57 discharges through R101, keeping the
output of comparator IC17B at the voltage acquired by C55. After approximately 10.4 ms, C57
will have discharged below the comparator trip point. The comparator output goes low,
discharging C55 and the circuit is ready for the next source pulse cycle.
Refer to 2754-03 schematic sheet 4.
The temperature of the system directly affects its ability to accurately measure CO
therefore must be precisely maintained at a controlled value. Two separate heaters and control
circuitry are used; one regulates the temperature of the detectors for the CO
reference channels; the other regulates the temperature of the transducer case (and loosely
maintains the temperature of the airway adapter). While the purpose of the detector heater is
to keep the detectors' sensitivity to infrared radiation constant, the function of the case heater
is to keep condensation from forming on the airway windows by elevating the window
temperature above the ambient airway temperature. Both heaters use an efficient pulse-width
modulation scheme designed to decrease power consumption, with the PWM timing generated
by the TPU under microprocessor control. This control loop is run by the CPU which does the
calculations and passes the duty cycle to the TPU. For the purpose of describing the regulation
loop, the case heater circuitry will be considered. The detector and case heater circuitry are
identical.
Inside the CAPNOSTAT
module. Initially, the CAPNOSTAT
®
CO2 sensor, a sensing thermistor is thermally connected to the heater
®
CO2 sensor is at the ambient temperature and the
resistance of the thermistor is large. A small current flows through the signal path
“CASETHERM” and only a small voltage is developed across R117. The microprocessor
programs the TPU to allow a maximum duty cycle of 90% to power the PWM heater circuitry.
This causes the heater control MOSFET Q9B to be pulsed on and off with a duty cycle that is
under direct control of the program software. As the heater warms up the case, the thermistor's
resistance decreases, raising the voltage appearing at the input of the control loop. As
described below, the MPU looks at this voltage and decreases the duty cycle of the PWM
control circuitry, gradually reducing the power output into the heater. When the desired
temperature set point is reached, a balance is struck between the energy delivered to the
system and the heat flow out of the system.
The case thermistor is sensed by amplifier IC18A pin 3. The difference between the signal at
the non-inverting input and the reference appearing at the inverting terminal generates an error
voltage proportional to the sensed temperature at the amplifier's output:
and
2
data and
2
e
(V) = [83.133V / (Rth+3.32K)] - 10.2V where:
o
= amplifier output voltage
e
o
R
= resistance of the thermistor = 4.36933K at 45°C
th
°
Te m p (
where e
C) = 4.1288 (°C/V) * e
= amplifier output voltage at temperature T
o
V + 41.7321°C
o (T)
This error voltage is low pass filtered by amplifier IC20A, sent to the ADC (IC6) and processed
by the CPU to regulate the output pulses from the TPU. The TPU PWM signal is buffered by
MOSFET Driver IC19A and capacitively coupled to the gate of the heater drive MOSFET, Q9B.
Capacitive coupling the signal prevents a system fault that would allow the PWM to be stuck at
a level that would cause too high of a heater output. In the absence of a pulse, the gate drive
Rev. 00 Model 615 Service Manua
15
Section 3
Theory of Operation
will be pulled high, disabling the output to the heater. The pulsed voltage signal out of the
MOSFET is filtered by D12, L6, C68 and C69 to produce a DC output level for the heater. Since
the TPU generated PWM signal is based on the system clock, it is synchronized with the
generation of the source pulse timing. This minimizes the effect of any random disturbance
caused by the heater circuit on the detection of the CO
data and reference signals.
2
The error voltage out of amplifier IC18A also appears at the temperature watchdog comparator
IC17C. If the error voltage reaches a voltage equivalent to 56 degrees Celsius, the comparator
trips, turning Q10 off. The gate of MOSFET Q9A is pulled high by R116, which turns it off and
VHTR is prevented from reaching the source of transistor Q9B. The temperature of the sensor
is also monitored by the MPU which will disable the heater when a temperature of 50 degrees
Celsius is exceeded. To shut off the heater, the MPU asserts the CASEOT signal, turning Q11
on which turns Q10 and Q9A off.
CO2 Input Signal Path
Refer to 2754-03 schematic sheet 5.
The signals from the sensor “CO2DATAIN” (CO
have similar signal paths. The CO2DATAIN passes through a high pass filter with a gain of 3.8
consisting of C80, R148 and buffer amplifier IC21B. The signal is fed to a Butterworth low pass
filter IC21A and associated components. This filter has a gain of 2 with a corner frequency of
1.5 KHz. The output from the low pass filter is fed to a 12-bit digital to analog converter IC22.
The signal, “CO2DIN” comes into the reference of the DAC, which acts as a programmable gain
stage followed internally by an amplifier with a fixed gain of 2. Here under processor control the
signal's gain is adjusted to an acceptable level for conversion. The gain setting is adjusted using
the digitized signal out of the A/D Converter (IC6) as part of the feedback loop. Similarly,
“CO2REFIN” is conditioned by high pass filter IC21D with a gain of 1.75 and low pass filter
IC21C with a gain of 2. The equivalent fixed gains for the two input signals are not equal in order
to compensate for differences in the output signal levels of the infra-red detectors in the sensor.
The output from IC22 is buffered by IC24A and AC coupled through C91 to IC23A. The
“CO2DATAIN” signal received from the sensor is ac coupled prior to the initial gain stage and
high pass filtered to remove any DC bias by C80. Prior to sampling CO
(Auto Zero) pulse biases Q15 on, causing any residual charge on C91 to discharge to ground.
At the start of the source pulse, the “CO2AZ” pulse goes low and the CO
is attained, and appears at the input of the sample and hold amplifier, IC16B. Near the end of
the source pulse, the “SS*/H” (Signal Sample and Hold) goes low and the peak signal is
acquired on the internal sample and hold capacitor. “SS*/H” returns high at the end of the cycle,
and the CO
signal on the sample capacitor is held at the peak value. The signal then passes
2
through a low pass filter of R159 and C92 before being converted by the ADC into digital data
and analyzed by the processor. The signal “CO2REFIN” follows an identical zeroing and
acquisition path.
Data) and “CO2REFIN” (reference signal)
2
signal, the “CO2AZ”
2
signal from the sensor
2
CAPNOSTAT
®
CO2 sensor
Interface
Refer to schematics 2754-03 sheet 5 and 2753-03 sheet 1.
®
Twenty pins of 60 pin connector J404 interface the CAPNOSTAT
CO2 sensor with the system
electronics. Ferrite and L-C filters have been placed on selected lines to suppress radiated EMI
and reduce susceptibility from external sources of interference.
Barometric Pressure Circuitry
Refer to 2754-03 schematic sheet 6.
Model 615 Service Manual Rev. 00
16
Theory of Operation
Sampling Pump
Section 3
IC28 is a piezoresistive differential pressure transducer with port P2 held as close to 0 psi (a
perfect vacuum) as is possible. It measures the absolute pressure difference at port P1 relative
to the vacuum at port P2. The transducer is calibrated for a full scale output of 0 to 15 psi, has
internal temperature compensation and is designed to be driven by a constant voltage source.
Instrumentation amplifier IC30 conditions this signal to correspond to the current barometric
pressure, which is set by adjusting VR1. The nominal gain of this amplifier is 93.56, which
corresponds to an ADC count of 3800 at 760 mmHg. The output signal from IC30 is low pass
filtered by IC29A and appears as an input (ABPRESS) to the 12-bit ADC.
Refer to 2754-03 schematic sheet 2.
To enable the monitoring of non-intubated patients, a single tapered sampling port is provided
on the sensor interface panel. Voltage regulator IC49 adjusts the pump motor speed to set the
flow rate of air through the tubing system for 180ml/min. Resistor’s R275 and R277 set the
voltage to approximately 2.5V. VR2 is a potentiometer in parallel with R277, which can be
installed if more accuracy is required for a flow rate adjustment. Pump motor current is sensed
by measuring the voltage developed across resistor R278 using amplifier IC50 that provides a
gain of 63. This provides an output of 8mA per 1/2 Volt {
ADC, or approximately 2.5 uA per bit resolution {Vref
31 Hz filter composed of IC29B provides high frequency attenuation. The VPUMP signal is
digitally converted by IC6 and monitored by the processor.
= (I
o
/ (212*Gain)}* {4mA/V}. A two-pole
(ADC)
*R) / Gain} into the 12-bit
pump
Digital and Analog Control Lines
Refer to 2754-03 schematic sheet 2.
IC10 is enabled by the LATCH2_CS* line from the processor, the D8-D15 data lines then control
the following signals:
SPO2CAL Not used
SPO2SC1 Not used
SPO2LPON Not used
INSIG Not used
SIGND Not used
BACKLIGHT Used with LITE_CLK for display’s backlight control
POWER_ON Powers the monitor down (active low)
PUMP_CTRL Controls sampling pump
Analog signals in the system are converted to digital values by IC6 then analyzed by the
processor
CO2DATA CO2 data channel
CO2REF CO2 reference channel
CO2ISRC Current through CO2 sensor’s source
CO2CASE CO2 sensor case temperature
CO2DET CO2 sensor detector temperature
ABPRESS Barometric pressure
SPO2FEDC Not used
Rev. 00 Model 615 Service Manua
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Section 3
Theory of Operation
SPO2IRLED Not used
SPO2IRLED Not used
VPUMP Monitors current through the sampling pump
VBATTADC Battery voltage level
3.3 Power Supply and Battery Charger
Supply and Reference Voltage Generation
Refer to 2754-03 schematic sheet 8.
The monitor operates from either an isolated external DC power supply or from the internal
battery. There are two options presently for the internal battery, a Nickel Metal Hydride battery
pack (NiMH), or a Disposable AA Lithium cell pack. The NiMH battery pack operates from a
nominal voltage of 7.2V down to 6.0V while the AA Lithium pack operates from 10.5V down to
6.0V. This battery voltage range is monitored in hardware by the 12-bit ADC for level and
comparator IC37A in order to shut the unit down at approx. 6.0V. The NiMH battery can be
charged either externally via a separate charger or internally when the DC input is connected
and a NiMH battery is installed. The internal battery charging circuitry is located on the 275301 assembly and is described in a later section of this document. The Lithium battery pack has
a schottkey diode in series with the positive battery terminal to prevent accidental charging of
the Lithium cells.
The core of the power supply design for the system is a 500 KHz switching regulator, IC36, that
utilizes a flyback transformer configuration to generate the analog DC supply voltages. The
primary of the transformer is designed to accept 6.0 to 13 V DC input and provides secondary
outputs of nominally +13.75VDC, and -13.75VDC which are regulated by R204 and R210 off of
the +VA supply. These supplies (±VA) feed all of the analog circuitry in the monitor. All supplies
are L-C filtered to minimize noise in the analog front end. An additional switching regulato
(IC41) generates the 5VDC supply (VDD) which feeds all the logic circuitry in addition to a
filtered version (CVDD) which supplies the logic level requirements of the CO
data converters e.t.c.). The 5V supply is L-C filtered to provide clean logic supplies for the
analog sections of the CO
clean, well regulated supplies (±CVA) for the CAPNOSTAT
designed as a tracking regulator pair to provide a 24VDC differential voltage for powering the
CAPNOSTAT
®
CO2 sensor source (+VSRC, -VSRC). Power for the CAPNOSTAT® CO2 sensor
(CVDD) system. IC35 and IC40 are linear regulators which provide
2
®
CO2 sensor. IC38 and IC39 are
heaters is supplied by VDCIN for maximum efficiency.
signal path (i.e.
2
Model 615 Service Manual Rev. 00
18
Theory of Operation
Section 3
Refer to Table 6 for power supply breakdown.
Table 5: Power Supply and Reference Outputs
Signal Supply Description
VDCIN +6.0 V to +13 VDC Main DC input generated from external DC input or inter-
nal battery.
VBATT +6.0 V to +10.2
VDC
VBACKUP +2.5 VDC or +5
VDC
VHTR VDCIN
Internal battery DC input, max level dependent on battery
installed.
Supply for SRAM and real time clock, either VDD or 2.5V
to maintain SRAM data during power down.
Supply for the CAPNOSTAT
®
CO2 sensor case and
detector heaters, supplied by battery or external DC input.
When powered by battery heater power follows input
power.
VDD +5 VDC Regulated digital logic supply .
CVDD +5 VDC Regulated and filtered logic supply for CO
analog front
2
end.
+VA +13.75 VDC (nomi-
Tightly regulated +13.75V DC supply.
nal)
+CVA +12 VDC Linearly regulated and filtered positive supply for the
CAPNOSTAT
®
CO2 sensor and CO2 front ends.
+VSRC +12 VDC Linearly regulated and filtered positive supply for the
®
CAPNOSTAT
CO2 sensor source. Tracks -VSRC to pro-
vide a 24V +/- 2.5% differential voltage across the source.
-VSRC -12 VDC Linearly regulated and filtered negative supply for the
CAPNOSTAT
®
CO2 sensor source. Tracked by +VSRC to
provide a 24V +/- 2.5% differential voltage across the
source.
-VA -13.75 VDC (nomi-
Loosely regulated off of the +13.75VDC feedback line.
nal)
- CVA -12 VDC Linearly regulated and filtered negative supply for the
®
CAPNOSTAT
CO2 sensor and CO2 front ends.
CVREF +2.5 VDC Buffered reference for the A/D converter.
2CVREF +5.0 VDC
Buffered reference used in the CAPNOSTAT
®
CO2 sen-
sor heater control circuitry.
-2CVREF -5.0 VDC Buffered reference used for the contrast control circuitry.
VREFO/2 +1.25 VDC Buffered reference used for DC excitation for the baro-
metric pressure sensor
Rev. 00 Model 615 Service Manua
19
Section 3
Theory of Operation
Table 5: Power Supply and Reference Outputs
SPO2VLED 0 to 2.5 VDC Not used
VDISP -6.5 to -11.5 VDC Negative bias supply for the LCD used to adjust the con-
trast level.
Refer to 2754-03 schematic sheet 6.
Stable reference voltages for the sensors and analog circuitry are derived from IC25, a
precision 2.5V reference generator with low drift. Five (2CVREF) and 2.5 Volt (CVREF)
references for the CO
circuits are generated by IC27, while a separate –5.0 Volt (-2CVREF)
2
supply is generated directly from IC31A for –VA and -VD on the 20 bit ADC’s for the saturation
front end.
Refer to 2753-03 schematic
When the monitor is operated from the DC input power source the green AC ON indicator on
the front panel is lit. If DC input power is lost or is not available, the monitor automaticall
operates from its internal battery without interruption. The AC ON indicator is extinguished and
a BATTERY LED on the front panel lights up, indicating the current voltage level of the battery.
While on internal DC power, the current state of the battery is monitored by both software and
hardware (IC37 2754-03 schematic sheet 8). Should the battery power level get critically low,
the monitor software alerts the user. If the monitor is not placed on external DC input power
within approximately five minutes, the software will shut the unit off. Should the software fail to
turn the monitor off when the low battery alarm sounds, the hardware cutoff (IC37A) activates
(+VBATT=6.0V), turning the unit off. The trend memory data stored in SRAM is retained by the
presence of VBACKUP power which is generated by a 3 Volt on-board Lithium battery.
Battery Charger Circuitry
Refer to 2753-03 schematic sheet 1.
The internal NiMH battery (7.2V, 3Ahr) will charge when the monitor is connected to the external
DC power supply (9220-10) or installed in the Base Station option (PN. 6998-00) with the
external adapter connected to the Base Station.
Battery charging is controlled by IC1, a frequency modulated fast charge controller. IC1
monitors temperature, voltage, and time throughout the charging process to safely and
effectively charge the internal battery. The charger is configured to terminate charging using the
(delta temperature/delta time) method of charge termination. Charging is maintained at the C/
4 (750mA) rate while current to the battery is controlled by Q1, Q2, Q3, and the “MOD” output
of IC1. Q3 provides base drive for Q1 while Q2 serves to shut Q1 off very quickly on a cycle by
cycle basis, allowing the large currents required for charging to pass through Q1 which is a
surface mount SOT-23 package PNP transistor capable of 500mW’s of power dissipation.
Charge current is monitored at the SNS input (IC1/9) and is set by R13 (I
2*R
). Temperature is monitored using the battery’s internal thermistor, in conjunction with
SNS
R9, R10, and R12. R9, R10, and R12 set the deltaT/dt charge termination parameter to 1°C per
minute. R7 and R8 set the maximum temperature for charge termination (a safety override) to
45°C.
Battery charging is initiated in one of two ways: either by applying 13.0 VDC to +VCHG,
therefore providing VCC (BVDD) to IC1; or by inserting a rechargeable battery into the battery
compartment. Resistors R2 and R4 form a divider which sets the battery voltage window. If a
battery with a voltage below the lower threshold (V
, end discharge voltage, V
EDV
0.4*BVDD +/- 30mV or, 2.04V, +VBATT = 5.26V) is installed, the charger will remain in
maintenance mode until the threshold is reached. Conversely, if the battery exceeds the upper
= 0.2225V/
REG
EDV
=
Model 615 Service Manual Rev. 00
20
Theory of Operation
Section 3
threshold for maximum cell voltage (V
, maximum cell voltage, V
MCV
= 0.8*BVDD +/- 30mV
MCV
or, 4.08V, +VBATT = 10.5V), charging will terminate. After fast charge is terminated, either by
deltaT/dt or by time-out, the charger switches over to a maintenance charge of C/64 to keep the
battery topped off. BVDD (VCC for IC1 and D4, the AC on indicator) is regulated by D10, a 5.1V
zener diode, while R3 keeps D10 operating in the knee region and C5 and C6 provide filtering.
Over-current protection is provided by F1, a 1A slo-blo replaceable fuse. Reverse leakage
protection is provided by D5 and D6 which prevent the battery from trying to power BVDD and
+VCHG in the battery operation state.
Rev. 00 Model 615 Service Manua
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Section 3
Theory of Operation
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Model 615 Service Manual Rev. 00
22
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