ADS7951: Could you help to check the OPA design for ADC?

Hi Qin,

It looks like U19 is acting as a comparator and will output 5V when the input to the OPA is above 0V. You stated above that you wish for it to act as a buffer.. which is the case?

With the output of the OPA at 5V, this is above Vref. This will saturate the ADC. If you can provide some more clarification on the use of U19, that would be great. I am also a bit confused on what you mean by the ADC input: 1mV ~5V. Is that the range the ADC will see?

Regards,

Aaron Estrada

HI Aaron

Ah, U19 use for buffer, it should be out = input, so u

19 have a wrong  connection, I think U19 pin2 should be connect to pin6, not  GND. 

Aaron 

I am also a bit confused about what you mean by the ADC input: 1mV ~5V. Is that the range the ADC will see?

Qin>> I think ADC will see 0~5V in spec(0~2*Ref, Full-scale)

Our voltage which input ADC should be From 1mV to 5V(Maybe From 10mV to 5V)，When the input is 1mV, I think we need U18 Gain>100.

Qin

Like this：

Hi  Aaron 

Could you help to check?

Thanks

Qin