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Part Number: ADS8688
I am testing our ADS8688A EVM and my input signal is a DC voltage from 0V to 5V.
Use the input range of 0~5.12V,
connect the OPA2209 filter between input DC signal and ADC input pin. then the ADC output error is extremely larger: 2V DC Vin, ADC output 1.698V, as shown in following picture.
Here is some test results during debug.
The voltage in A0+ of J25 is 2V DC, but voltage in J8 pin is 1.69V, so the ADC input pin voltage is 1.69V.
So I think this error between 2V and 1.69V ADC output is come from OPA2209 circuit, but this is only a 2nd order LPF.
Can you give me some help on this issue? Thank you!
By the way, when I direct input the signal to ADC input pin, there is not so much error.
Did you apply external high voltage power supplies (EXT_HVDD and EXT_HVSS) on J12 and J14? or did you just use 5V_SDCC from SDCC card?
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