Mindray DPM 1 Manual de servicio descargar pdf (Pagina 19)

Circuit Principle

2-7 Pulse oximeter Service Manual

2.1.1.10 Voltage Detect

DPM1 requires that the battery voltage and +7V be detected all the time. S1C33209 has 8

10-bit AD channels, two of which were used. S1C33209 cannot stand that high voltage, so,

a voltage divider was adopted to convert the monitored voltages to the range S1C33209

can detect. The divided voltage has a RC filter, which can resist the influence from

electrostatic charge.

2.1.2 Power Supply Circuit Block Diagram

Fig 2-10 Power Supply Circuit Block Diagram

2.2 Reliability Design

The following reliability control methods are used in the DPM1:

1. Derating for key elements;

2. Watchdog circuit, to restore the system when the software crashes;

3. By-pass capacitors for each IC, to reduce the interference from power supply;

4. Serial resistors on each line of the serial port, to avoid the destroy to devices due

to unintentional short with power;

5. One I/O port to control the write protection of the FLASH, to reduce the possibility

of unintentional FLASH write;

6. Monitoring the two major voltages through the CPU’s AD, to prevent inaccurate

measurement and unreliable data due to the voltage swing.

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Mindray DPM 1 Manual de servicio Pagina 19