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TPS40170 recovery from a output short circuit.

George Chen
Intellectual 2175 points
Other Parts Discussed in Thread: TPS40170

Team,

TPS40170 convert 35V to 24V at 100kHz and 47uH choke with a 1uF SS cap.

While we test a short circuit at output, the TPS40170 is not able to recovery while removing the short circuit.

But if we remove the output capacitance 3000uF, the circuit can recovery from the short circuit.

Or no removing the Cout, but reduce the full load current from 7A to 1A, the circuit can also recovery.

May I know if there is any limitation to cause this happen?

Thank you.

  • 0
    TI__Mastermind 35165 points

    Hi George,

    Could you share the schematic?

    I have some thoughts but it would be best to get a couple waveforms to confirm. For the three scenarios described can you get waveforms showing VOUT, SS and SW? The three scenarios are no 3000µF capacitor, 7A load with 3000µF capacitor and 1A with 3000µF capacitor.

    It would be good to include two different time scales. One with a large time scale to show the entire hiccup time period. Second with a smaller time scale to show individual switching cycles when the TPS40170 stops switching and starts hiccuping.

    Start up into high prebias output voltages may cause the TPS40170 to trigger short circuit protection during start up. When the TPS40170 hiccups the high prebias output voltage can occur in this test condition due to the large amount of capacitance and high output voltage. What this can cause is not enough voltage across the BOOT capacitor resulting higher Rdson of the high-side MOSFET when the TPS40170 starts switching. SCP uses high-side MOSFET Rdson sensing so the higher Rdson can trigger SCP.

    Best Regards,
    Anthony