LT4256 hot swap controller enable/disable

Discussion created by steechung on Feb 1, 2018
Latest reply on Feb 5, 2018 by DEddleman

Has anybody used the LT4256 hot swap controller as an electronic circuit breaker? I have simulated and designed a board that is essentially identical to the evaluation module (resistor scales are different due to different source voltage). I am trying to enable (turn on or off) the LT4256 by pulling UVLO pin low using an external MOSFET circuit, similar to Fig 11 of the datasheet (see link below). 


Test Setup:

I have a 36V source (battery) connected to the input, and a 32 Ohm power resistor load. When closed, the resistor draws a little over 1A. An MCU toggles the external MOSFET gate low to attempt to open the larger series NMOS. 



When I attempt to connect the MCU GPIO to the MOSFET gate, the LT4256 IC heats up to over 100C (verified using a thermal imaging camera). When I disconnect the MCU control signal, the LT4256 cools down and seems to operate properly. 


Any thoughts or suggestions? I will test again soon, but with a manual short across UVLO. I realized may not be controlling the FET with a high enough gate voltage. Thank you!



Useful links:

lt4256 datasheet

lt4256 evaluation module