Main Unit Theory of Operation
1 - 6 0070-10-0705 Passport V™ Service Manual
Speaker
The speaker provides sound for alarms, key strokes, heart beats, pulse, and so on. It is driven
directly by the CPU board.
AC and battery status LEDs
The AC status LED and the battery status LED, located at the keypad, are controlled by the
MCU on the power management and interface board. The driving signals come from the
power management and interface board and then go to the keypad via the CPU board.
1.3.3 Processing and Communications System
CPU board
The CPU board is the heart of the patient monitor. It implements a series of tasks including
input and output control, data storage and processing, display processing, system control,
communication management, print management, alarming, etc.
The CPU board has a CPU system comprising the CPU, FLASH, memory, real-time clock,
EEPROM, FPGA, etc. Among them, FPGA deals with audio, video, and interfacing signals.
Also, it provides interfaces to other boards, modules, and devices.
Connections and communications with other components are implemented via the CPU
board, which provides interfaces to:
•A built-in display
•The power management and interface board. Between this board and the CPU board,
the signals of USB+Network+UART+SVGA+I2C+Speaker+GPIO are communicated.
Among them, UART signals finally go to the parameter boards.
•The keypad. Between the keypad and the CPU board, there are two signal wires: one is
the UART signal wire and another is the AC power and battery status signal wire.
•The alarm LED board
Power management and interface board
The power management and interface board is a multi-functional board. It transmits UART
signals to several boards and modules (e.g., multi-parameter board, CO
2
module, OEM
SpO
2
module, NIBP module, recorder module, etc.).
1.3.4 Power Management System
Battery
The monitor uses two rechargeable lithium-ion batteries (11.1 V, 4400 mAh). The battery
compartment door is located at the left-bottom of the patient monitor. The battery power is
introduced to the power module via the battery interface board, and then processed and
distributed to each component by the power management and interface board.
Battery interface board
The battery interface board serves as an interface between the batteries and the power
management and interface board.
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