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LTC4371 as low-side ideal diode in positive voltage protection: FaultB pin doesn't seem to work

Dear Power by Linear,

     I would like to use the LTC4371 in an electronic load, as an ideal diode in series with the return (negative input) from the device under test. I still haven't been able to upload a .asc file, so here's a screenschot.

When the voltage at (LOAD+ to LOAD-) reverses, the LTC4371 turns off the pass FET M1 just like it should. But the FaultB pin never goes low. I'd like to use FaultB to signal the other circuits that a reverse voltage has been detected. Any idea why it doesn't change state?

Many thanks,

Chris

  • Hello Chris,

    Please note that the LTC4371 FAULTB pin does not indicate a reverse current condition. It indicates if any of the MOSFETs’ on-resistance has degraded to a high value (datasheet: page 5 definition, page 7 last paragraph, page 13). It does that by monitoring voltage drop from source to drain (ideal diode forward voltage drop) when MOSFET gate is fully on. If the forward voltage drop exceeds 200mV with an on MOSFET, FAULTB pulls low.