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

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

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