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ADS131A04: Power supply topology for 0V center

John Fedak
Expert 6715 points
Part Number: ADS131A04
Other Parts Discussed in Thread: TIDA-00835

Hi Team,

I'm working with a customer that is designing with the ADS131A04 and they are interested to use the internal charge pump to remove complexity, however they are also interested in keeping the ADC 0V centered.

Based on the datasheet, if the internal charge pump is used, the device will go from -1.95 to 3.3V. I noticed in the TIDA-00835 reference design, for bipolar inputs an external 2.5 and -2.5V rails are provided.

With all of this, I'm guessing this is not possible and external supplies are necessary for the device to be 0V centered, can you confirm?

Thank you!

Regards,

~John

  • 0
    TI__Guru**** 168445 points
    Hi John,

    For the ADS131A04, what sort of input voltage do you intend to apply to the ADC? Even with -1.9 and +3.3, you can center the input on 0V depending on your input signal magnitude and gain settings. There is no way to boost the -1.95 to -2.5V on chip.
  • 0 in reply to Tom Hendrick
    Prodigy 20 points

    Hi Tom,

    We are flexible with our input voltage.  Within -5V and +5V would work for us, but would like to center the input on 0V.  
    We are planning to use 128ksps at 15.62 effective bits - (Gain = 1).

    Can you explain how we can center input at 0V with -1.9 and +3.3 power supply?

    Thanks,
    Jon

  • 0 in reply to Jonathan Li
    TI__Guru**** 168445 points
    Hi Jon,

    Thank you for the added detail and my apologies for the delay in getting back to you. You can apply an analog input as high as +/- 1.5 V (centered at 0 V) when using a 3.3 V supply and the internal negative charge pump. To get the highest dynamic range though, you would need to look at a -2.5V rail using an external supply similar to the configuration John mentioned with TIDA-00835.