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ADS8910B: Question about the 100mOhm Resistor in Layout Example

Michael Persang
Prodigy 20 points

Part Number: ADS8910B

Hello,

i am currently designing a board with the ADS9810B and was wondering about what the 100mOhm resistor in between the REFBUFOUT and CREFBUF in the reference layout on page 66 of the datasheet does.

Is it just to guarantee a minimum dampening to prevent internal oscillation?

And about the wide copper plane underneath the REFBUFOUT - side. Does it need to be that broad or can it be slimmer?

Thanks in advance!

Kind Regards

  • +1
    TI__Guru 51060 points

    Hello Michael,

    Welcome to the TI E2E community!

    Yes, the series resistor helps with ringing/stability of the internal reference buffer.  This resistor is not necessary, but including it will help improve overall noise performance of the ADC.

    The wide copper pour is intended to reduce total inductance in the Cap+resistor connection.  You can reduce the size of this pour if needed.  Moving the capacitor and resistor as close as possible to the ADS8910 package will result in best overall performance.

    In both cases the ADC will still function correctly, but adding the resistor and keeping the inductance low will help minimize total ADC noise.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Prodigy 20 points

    Thank you very much for the detailed answer!