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PGA280: Power supply decoupling

Benjamin Bawkon
Expert 1085 points
Part Number: PGA280

Hello TI,

The PGA280 datasheet recommends R/C filters on each of the supply pins, however the example in the datasheet and the EVM both have VSON directly connected to ground with no series resistance.

For best performance, when using a true bipolar supply (+/-2.5V), is series resistance suggested on VSON (something like 10 Ohm/0.22uF), or should it be directly connected to -2.5V with just a decoupling cap?

Thank You,
Ben

  • +1
    TI__Guru 54996 points

    HI Ben,

    In the case of an unipolar VSOP=+5V and VSON=GND, there is no need to use a decoupling capacitor on the VSON pin, since this will normally connect directly to the GND plane of the PCB board. 

    In the case of bipolar output supplies, VSOP=+2.5V, VSON=-2.5V, the VSON pin requires the local bypass decoupling capacitor.  The datasheet recommends a local bypass capacitor and suggest a 10Ω series resistor as a filter.  The optional series resistor/filter can be helpful to reduce supply noise.

    The best practice is to use low-noise, stable, linear supplies and keep noise sources away from the sensitive analog signal chain circuits. Use bypass capacitors in very close proximity to the PGA280 supply pins.

    Thank you and Regards,

    Luis