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TPS54361-Q1: Output Short-Circuit Current

Shinichi Yokota
Genius 9715 points
Part Number: TPS54361-Q1

Hello,

I guess the output current of a TPS54361-Q1 supply circuit will be reduced when the output is shorted to GND because of the TPS54361-Q1's switching frequency foldback function, but how small can the output short-circuit current be when the load is ideally 0 Ω?

When a short-circuit event happens, I guess the switching frequency is decreased to one eighth (1/8) and the duty cycle is reduced to its Min on-time, but how much can the output  short-circuit current be, in other words?

Best regards,
Shinichi Yokota

  • +1
    TI__Genius 13310 points

    Hi Shinichi,

    The datasheet states that the device will hit the maximum current limit value then slowly discharge the inductor current by turning on the low side FET.

    The value of this current limit is listed in the EC table:

    For this device, it could be up to 6.8A maximum.

    Thanks,

    Andrew

  • 0 in reply to Andrew Kutzler
    TI__Genius 9715 points

    Andrew,

    The data sheet implies on page 21 that the output current is reduced after it hits the current limit threshold. My question asks how small the output current will be when the output voltage is forced to 0 V (0 Ω).

    Does your answer mean that the output current will continue to hit the current limit threshold until the cause of the short-circuit event is removed?

    Best regards,
    Shinichi Yokota

  • +1 in reply to Shinichi Yokota
    TI__Genius 13310 points

    Hi Shinichi,

    The output current will reach the current limit specified by the device. Then the low side FET will turn on and slowly the current will decrease in the inductor. Afterwards the high side FET will turn on again, and current will increase in the inductor (which may exceed the peak current limit if minimum on time is too long).

    Basically, the device will keep attempt to provide as much current as possible before hitting the current limit every cycle. This is the relevant text from the DS:

    "During overcurrent conditions that pull the output voltage low, the error amplifier increases switch current by driving the COMP pin high. The error amplifier output is clamped internally at a level which sets the peak switch current-limit." p 21

    Thanks,

    Andrew