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ADS1120: Please check the schematic with internal voltage reference

Chase Jeong
Genius 4670 points
Part Number: ADS1120

Hello TI experts,

My customer consider ADS1120 for their new product, and they want to check their schematic.

they designed as bipolar operation, DVCC=3.3V, AVDD=+2.5V, AVSS=-2.5V.

and they want to use internal voltage source.

1. in this case can I use +/-2.048V as internal reference voltage?

2. can I leave REFP0 and REFN0 as floating in this case?

i will attach the schematic for your convenience.

please check this issue. Thanks.

Best regards,

Chase

  • 0
    TI__Guru** 112895 points

    Hi Chase,

    Yes, the ADS1120 internal reference is 2.048V which allows for a full-scale range of +/- 2.048V at a gain of 1.  You can leave analog and reference inputs floating.  This is discussed in the ADS1120 datasheet in section 9.1.5, Unused Inputs and Outputs.

    I did notice in your schematic that you have 0 Ohm resistors on the digital pins.  TI recommends resistors around 47 Ohms to reduce noise from clocking and sharp edges of transition.

    Also notice information given in the Pin Functions table on page 4.  For the center pad of the QFN package you should either leave this pad floating or connect to the lowest potential which would be AVSS.  So either leave the pad floating or connect it to -2.5V.

    Best regards,

    Bob B