IMP23ABSU hardware interface

[NCatt.1]

Hello, 

I have as project to use the STWINKT1B board and write my custom code to read IMP23ABSU sensor at its maximum capacity (80kHz). I understand the sensor output data is amplified by an op-amp and can be read with ADC input of the microcontroller, but what is the exact interface ? I don't really understand the schematics logic of the sensor (Why is there 2 ouputs: "MREF" and "M1P_FILT", why are 2 op-amps used)

Could you please give me more details ?

Then, is there some basic examples of how to read the sensor ? ADC input configuration, sensor configuration, reading...

Thank you

[Federica Bossi · Accepted solution]

Hi @NCatt.1 ,

The circuit of that amplifier is used to centre the signal around Vdd/2, to exploit the full dynamics of the microphone up to the AOP (acoustical overload point). The MREF_DIV is in fact obtained by halving Vdd of the Mic with a divider, and through the buffer configuration the output MREF follows the input signal. The M1P_FILT signal, on the other hand, is precisely that of the microphone, which passes through an amplifier in a non-inverting configuration, with amplification factor 1 + R6/R7 = 2.34. This amplification factor is to take advantage of the microcontroller's 3.3V. The micro's ADC then acquires on IN1 the reference Vdd/2 and on IN2 the amplified signal centred around Vdd/2.