-URGENT- AD7688 analog input is instability.

Hi

We're facing a issue that the analog input is instability below.

CH4 is IN+. CH3 is SDO.

Actually the driver amp is OPA197 (Ti), we recommend ADA4084-1 instead of Ti.

But the customer say if the instability is not improved within this week, he may use ADS8863 (Ti) instead of AD7688.

The input+ is DC voltage and the input- is GND as single input.

Could you please give me any advice.

Thank you very much in advance.

OPA197

http://www.ti.com/product/OPA197?keyMatch=OPA197&tisearch=Search-EN-Everything

ADS8863

http://www.ti.com/product/ADS8863?keyMatch=ADS8863&tisearch=Search-EN-Everything

 

Regards,

Hiroyuki

Parents
  • +1
    •  Analog Employees 
    on Sep 20, 2018 1:28 PM

    Hi Hiroyuki,

           The customer is having Vin+=DC voltage and Vin-= GND. What is the value of the DC voltage? This should work if Vin+= Vref. Please take note that the AD7688 is a differential ADC, it is expecting that the input of Vin+ and Vin- is opposite with each other and also take note of common mode voltage Vref/2, which means the difference of the Vin+ and Vin- should be within the common mode voltage.

       The customer may use AD7686, which is a Pseudo Diff ADC basing from the input voltage that you mentioned.

    Regards,

    Jonathan

Reply
  • +1
    •  Analog Employees 
    on Sep 20, 2018 1:28 PM

    Hi Hiroyuki,

           The customer is having Vin+=DC voltage and Vin-= GND. What is the value of the DC voltage? This should work if Vin+= Vref. Please take note that the AD7688 is a differential ADC, it is expecting that the input of Vin+ and Vin- is opposite with each other and also take note of common mode voltage Vref/2, which means the difference of the Vin+ and Vin- should be within the common mode voltage.

       The customer may use AD7686, which is a Pseudo Diff ADC basing from the input voltage that you mentioned.

    Regards,

    Jonathan

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