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TPS7A80: TPS7A8001 application question about capacitor

Dane Zhang
Expert 3470 points
Part Number: TPS7A80

Hi team,

The datasheet of TPS7A8001 states that no feedforward capacitor should be added, but we have added a 1nF capacitor (1005 package) in the schematic diagram. Please help to confirm whether there is a problem with adding this 1nF capacitor, thank you.

  • 0
    TI__Mastermind 29260 points

    Hi Dane,

    The feed forward capacitor installed in the customers schematic will result in an added zero at 1.59 kHz and an added pole at 5.67 kHz.  This is certainly within the bandwidth of the linear regulator and will impact the stability of the device.  As the datasheet explicitly states to not use a feedback capacitor here, I believe there is a chance that an instability could be seen with the 1nF feed forward capacitor.  I would depopulate it in the assembly process so the customer does not need to change any artwork going forward.

    Thanks,

    - Stephen

  • 0 in reply to Stephen Ziel
    TI__Expert 3470 points

    Hi Ziel,

    you mean add cap in R1 will lead to the zero and pole?

    datasheet only state that not add  cap in R2.

  • 0 in reply to Dane Zhang
    TI__Mastermind 29260 points

    Hi Dane,

    It looks like the datasheet has a mistake.  The feed foward capacitor would be across R1 in this schematic not R2.  I have added this to our datasheet correction log and it will be updated in the next revision of the datasheet.

    Thanks,

    - Stephen