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TPS54327: HS-FET - reverse current capability

JosefMieslinger
Intellectual 2170 points
Part Number: TPS54327
Other Parts Discussed in Thread: TPS54527

Hi Team,

my customer uses the TPS54327 and TPS54527 to generate the 3.3V rail in the system.
In the manufacturing process he will power the 3.3V rail from an external source to program the microcontroller while the remaining circuit stays unpowered.
When he is powering up the 3.3V at Vout rail while the Vin is unpowered, there will be current flow over the HS-FET to the Input rail.
What is the reverse current the TPS54327/TPS54527 devices can handle on the HS-FET without being overstressed?

Thanks!

Best regards,
Joe

    

 

  • 0
    TI__Expert 3480 points
    If Vin is unpowered, the input side is open. Why do you think it has a reverse current for HS?
  • 0
    TI__Expert 5745 points

    Hi

    We don't have this data, but normally, for 3A part, the body-diode can handle 3A. And this path will not last a big current because of the input cap. So don't worry about this if you don't connect a source at output to sink current.  

  • 0
    TI__Expert 4875 points
    Hi Joe,

    I think you could refer to the current limit in the datasheet for the max current capability of HSFET body diode. And since you have inductor in between input and output cap, so the current on HSFET body diode should not be a concern. The only concern is from the input UVLO. Your output voltage is only 3.3V which is below UVLO so the device will not start up after input cap is charged. You will not see any problem here. But for other condition like Vout=5V which is higher than UVLO. The device will start up and could bring trouble especially for FCCM mode device like TPS54327.