ADC input voltage question

6 years 11 months ago #930 by ucfanrg
Hi, I just received all the parts I needed to make an pedalshield. I think I might have bought the wrong parts because of this problem :
I just saw that the ADC input voltage for the STM32F103 is 3.3v, and the schematics suggest 5v.
is 5v really necessary, or can I just hookup 5v pins to 3.3v? Will I have to change component arround the TL072 and the TC1044?

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6 years 11 months ago #931 by Ray
Replied by Ray on topic ADC input voltage question
The DUE ADC span is 0 to 3V3, in the DUE we use 5V (+5 and -5 volts generated by the TC1044) in the op-amps to have plenty of headroom and avoid rail clipping.
The final signal delivered to the DUE ADC is no bigger than 3V3 (and if there is more voltage, the clamping diodes will protect the ADC).
If you just want to use 3V3 in the whole circuit you would need to use rail to rail op amps a redesign the circuit....

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6 years 11 months ago #932 by ucfanrg
Replied by ucfanrg on topic ADC input voltage question
No, I can use 5v in my circuit, just not on my ADC. I was worried that it would fry my pins, but thanks for the info!

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6 years 11 months ago #933 by Ray
Replied by Ray on topic ADC input voltage question
You have to be careful with the ADCs, there are two clamping diodes to avoid voltages over 3V3 on the ADCs.
The DACs are pretty sensible too, if you short them to ground they will blow too... there are also 2 caps to prevent this on the pedalSHIELD DUE.

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