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Load Switch or E-Fuse that completely disconnects output during short to ground

Other Parts Discussed in Thread: TPS25944L, LM76202-Q1

Hi Team,

Is there a device in our portfolio that will completely turn off the FET during a short to ground scenario on the output? All of the devices I am looking at use current limiting, which leaves the FET on during a short to ground. I can't seem to find one that completely cuts the power..

Please let me know if we have something. Thanks!

-Jared

  • Hi Jared,

    Our eFuses with latch-off variant, attempts one current limit operation immediately after short-circuit to make sure that the system does not remain in switch-off due to any transient overloads (similar to short-circuit). 

    Can you share some more details about this requirement? EE, application use case and why it is needed? 

    Best Regards, Rakesh

  • Hi Rakesh,

    Thanks for the reply. I think what I am looking for is called "circuit-breaker" per Figure 5 of this app note: https://www.ti.com/lit/an/slva862a/slva862a.pdf?ts=1623933153368&ref_url=https%253A%252F%252Fwww.google.com%252F

    Are there any automotive grade devices that implement the circuit breaker feature? This is for an automotive system where cabling leaves a module and is susceptible to short-to-ground conditions. The circuit requires that the current during the short be completely cut-off.

    Thanks,

    Jared

  • Hi Jared,

    We have TPS25944L, TPS26601 but these are not in automotive grade. 

    For Automotive, TPS25940L-Q1 and LM76202-Q1 are available but with current limiting  latch-off. Does these won't work ? Why circuit breaker is preferred while the current limiting also helps to limit the fault current in the path. ?

    Best Regards, Rakesh

  • Hi Rakesh,

    Thanks for the reply. The requirement is for the output of the E-fuse to be 0V. If the device is left limiting the current, there can be a significant voltage drop across a long cable if the short to ground is at the other end of the long cable, meaning that the output of the E-fuse won't be 0V. The latch-off feature won't work either because a the designer is not willing to wait until the device over-heats before it turns off.

    -Jared

  • Thanks Jared. Understood.

    One option is to use work around as below. For details please refer 10.2.4.3 Overload Detection Using TPS25940xx-Q1 in www.ti.com/.../tps25940-q1.pdf

    Best Regards, Rakesh

  • Hi Rakesh,

    Thank you for the solution recommendation! For this setup, when there is a short-to-ground/over-current condition, the PGTH/PGOOD function/output will turn on the FET, which will turn off the device. Then, because there is no current flowing, the PGTH/PGOOD function/output will turn off the FET, which will turn on the device, back into a short-to-ground condition. So will this behavior just repeatedly cycle? 

    Thanks,

    Jared

  • Hi Rakesh,

    Sorry. Correct, it will do ON/OFF cycling.. but since auto-retry is also needed here. we can modify that a bit.

    The R1*C sets the retry delay. 10 Ohm is to limit the current from C when the ext FET is turn-ON.

    ...

    The other option is to use PGOOD output with a latch comparator (controlling EN of eFuse) to keep the eFuse in OFF state.

    Please let me know your thoughts.

    Best Regards, Rakesh

  • Hi Rakesh,

    The R/C solution would help. For the PGOOD output with latch comparator, are you suggesting a discrete comparator?

    -Jared

  • Yes Jared.. a discrete comparator. Please suggest customer to give a try on the above R/C solution

    Best Regards, Rakesh