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TPS22918-Q1: VOUT Capacitor limit

Vishnu KN
Prodigy 20 points
Part Number: TPS22918-Q1

Hi,

As per datasheet, CIN greater than CL is recommended. To avoid current flow through the body diode from VOUT to VIN when the system supply is removed. 

In my design QOD shorted to VOUT for fast output discharge during Power OFF. Still the above statement is valid ? Since the output voltage will get discharged through the QOD pin instead of body diode?

More Info : 10uF connected to VIN pin and 1uF connected to VOUT pin of TPS22918-Q1 in my design. The VOUT goes to one PHY device IO Supply pin and PHY device vendor recommended to connect 47uF bulk cap. So 47uF connected to load side. Is this cause any issue ?

  • 0
    TI__Mastermind 19040 points

    Hi Vishnu,

    This recommendation is primarily application-dependent, so I recommend taking a look at the VIN and VOUT waveform when the supply is removed to be sure.

    If the input will be floating when the supply is removed, I think you should be fine as VIN will slowly dissipate, much slower than QOD. If VIN will be pulled to GND when the supply is removed, you might have some backflow, but if and how much will depend on the strength of pulldown on VIN and the load current on the output when the supply is removed.

    Thanks,

    Patrick