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UC2854B-EP: Maximum applicable voltage on VAO

Alexandre Gadois
Prodigy 10 points
Part Number: UC2854B-EP
Other Parts Discussed in Thread: UC2854B, , UC2845

Hi,

I am currently designing a PFC with a boost topology.

In my design, it is preferable to use an external op amp to do the voltage loop function,

The output of this external op amp is connected to the "VAO"  pin of the UC2854B. The "Vsense" pin is not connected at all.

The maximum applicable voltage on the "VAO" pin is not specified in the datasheet. Can I apply on VAO voltages up to UC2854B-EP "VCC" ? 

Thanks for your help.

  • 0
    TI__Genius 10555 points

    Hi Alexandre,

    The voltage error amp on the UC2845 is not a transconductance amp. If you try to force a voltage on that pin, the two amps will fight each other until one reaches it's current limit.  The best way would be to feed your external EA through a unity gain amp then into the VSENSE

    I hope this helps,

    Ray