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TPS7A8101-Q1: bypass capacitor and power stress

Part Number: TPS7A8101-Q1

Hi team,

in the datasheet, it recommend Cbypass=470nF.

1. when the output short(Vo=3.3V), the FB pin will go to negative voltage. will the FB pin have power stress risk? Cause, customer think Cbypass value is large. 

2. Do we have PSRR evaluation waveform under no Cbypass? 

  • Hi Mona, 

    Your customer is correct that Cbypass can cause the FB pin to be pulled too far negative in the event that a very fast transient (such as a short to GND) happens on the output. This is because Cbypass AC couples the FB node to Vout. If they are conerned about this they can either remove it (see the PSRR plots below) or decrease it to someting smaller like 10nF. 

    We also have an app note that covers the pros and cons of using Cbypass (often referred to as a feedforward capacitor), if they want to lear more.