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TPS51315 doesn't power up reliably

Cary Wright
Prodigy 10 points
Other Parts Discussed in Thread: TPS51315

Hello,

Our implementation of TPS51315 doesn't power up reliably unless we hold EN_PSV low while the input rails Vin and V5IN and V5FLT are ramping.

- If we hold EN_PSV low for 100ms until the other rails have ramped the power supply starts reliably.

- If we leave EN_PSV floating the power supply fails to start, it rings at startup and then hovers at around 200mv.

Is there any timing sensitivity of the input rail startup?

Regards,

Cary

  • 0
    TI__Mastermind 49430 points

    Hi Cary,

    TPS51315 has a timing sequence during start up.

    - If we hold EN_PSV low for 100ms until the other rails have ramped the power supply starts reliably.

    We recommend EN_PSV tied to GND before V5IN and VIN are stable, then connected EN_PSV to high for auto-skip mode or floating for FCCM mode.

    - If we leave EN_PSV floating the power supply fails to start, it rings at startup and then hovers at around 200mv.

    When you leave EN_PSV floating,  if  V5IN stabilized before Vin, the controller will consider UVP protection and latch off the output.  If the Vin stabilized before V5IN,

    it will be ok and the output will come up as long as V5IN reaches its UVLO threshold (around 4V).

    Thanks,

    Nancy