ADA4940-1  configuration

Dear sir,

I am using  ADA4940-1  for Single Ended to Differential for my Application.

I observed that ,when i gave  50mV to 1200mV as input and i got result  with less variations (uV variations). If i am trying to give >1200mV , i obeserved   big variation in the output signal (2mV to 8mV  ).

Please suggest suitable configuration for ADA4940-1 for measurement of 50mV to 2500mV.

  • 0
    •  Analog Employees 
    on Jan 24, 2018 7:24 PM

    Hi Dhanalakshmi,

    We can't be certain on what causes the variation you have observed unless you share to us your application. Schematic would be a great help for detailed analyses. What are your requirements? What would you like to do with the ADC driver? What signal are we dealing with? These information would be a good start.

    Regards,
    Jino

  • 0
    •  Analog Employees 
    on Jan 24, 2018 11:07 PM

    Hi Dhanalakshmi,

    Just to follow-up, what buffer are you using at the input of ADA4940?

    Thanks.

  • Dear Jino,

    Thank you for your Reply.

    Please follow  below Simplified  Schematic for my present configuration.

    1. Input Range is Uni-polar 0V to +3V Peak to Peak

    2. Unity Gain

    3. Uni-polar Supply Voltage ( 0V to +5V )

    4. Vocm  = 2.5V

    1. If there is any signal violation in above configuration? 

    2. I observed more than 8mV variation in the above configuration at input voltage >=2.5V   marked as Red in above Table.

    3. What is the maximum Peak-Peak  input  voltage support for ADA4940-1 SOIC  package (in Unity Gain Configuration) ?

    Please suggest the  recommended Schematic for measuring of 0 to +3V input range.

    Thanks

    Dhanalakshmi S

  • Dear Jino,

    Presently, We are using  AD8605 as a Voltage Buffer in  ADA4940-1 input  .

    Thanks

    Dhanalakshmi S

  • 0
    •  Analog Employees 
    on Jan 29, 2018 10:31 PM

    Hi Dhanalakshmi S,

    Upon reviewing your schematic, I see no violations in your configuration. However, I noticed on your results that some things are off the expected value. Did you use tight tolerances for your gain setting resistors? Let's take for example when your input is 1.260 V, VoP and VoN should be 3.13 V and 1.87 V respectively. But in your results, it's 3.094 V and 1.835 V. Could you also check the value of your Vocm, output of AD8031? The expected offset should not be above 1mV. See below figure for additional reference.

    Regards,

    Jino