
Circuit Principle
2-3 Pulse oximeter Service Manual
Fig 2-3 Data Storage Circuit
2.1.1.4 DAC
DPM1’s analog circuit includes two DAC channels. They are DRIVE channel and OFFSET
channel.
MAX5102A is a 8-bit resolution DAC control chip. The 2.5V reference level was produced
by MAX6066.
Fig 2-4 DA Circuit
2.1.1.5 ADC
DPM1 uses MAX1290 as the ADC, which of 12-bit resolution and 8 channels and parallel
interface. Two signals of SIGNAL and PROBE-DET are collected by the chip. They
directly enter the channel 0 and channel 1 of the ADC without analog switch.
MAX1290 uses separate power supply and the input signal should be in the range of
0V~5V. But the amplitude of the SpO2 signal is between -2.5V and +2.5V. Therefore, a
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