UC1843B-SP: External error amplifier to override internal error amplifier

Hey Stephen,

Most of the time the error amplifier is overridden with an external amplifier by forcing the COMP pin of the device with an external EA.

The VFB pin of the device can be connected to a stable voltage such that the internal EA doesn't interfere too much with the external EA.

I understand that the COMP pin doesn't have an explicit voltage rating, but I would suggest using the 6.3 V of VFB as the rating here as they are connected to similar rails.

Thanks,
Daniel

Would it be preferable to drive the internal EA output low or high to minimize its interference with the external EA?

Hey Stephen,

The output of the internal EA is what you would drive with the external EA, so no.

Thanks,
Daniel

Sorry, my question was badly written.  You suggested the VFB pin should be driven by a stable voltage so that the internal EA doesn't interfere with the external EA too much.  Since this will put the internal EA into open loop mode, a VFB above 2.5V will drive the internal EA output low and vice versa (VFB<2.5V, EA output goes high) - which state do you believe will interfere the least with the external EA's output trying to override the internal EA?  Sorry, it's hard to put that in words...