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UCC28070A PFC controller not working.

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Advanced Member level 5
Jun 13, 2021
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Have a daughter board containing the UCC28070A PFC controller. Want to test the UCC28070A before letting it loose on the PFC power circuit. It is not sending any gate drive pulses. Have fed it 12V. Its drawing 25mA as seen through the input 10R resistor, this seems a lot. Its got a correct 6V on its VREF pin. The Soft start capacitor isnt charging up....just stays at 0.9V or so. I did see ~6V on soft start cap at first but then never again.

There arent even any gate drive pulses when its first powered up. (did sample/hold on gate drive when powered up to prove this).

By the way, i have injected 1.9V on to the Vsense pin and onto the Vinac pin.

I have a properly working sync pulse circuit, but when i send those pulses to the UCC28070A , the sync pulse cct stops working....and it looks like voltage is being back-fed from the UCC28070A to the sync circuit.

Anyway, i also tried the UCC28070A in not_sync'd mode and it still doesnt work.

Being a hobbyist, i am not allowed on to the forum.
Do you know what might be wrong?

The datasheet doesnt say what voltages are needed to be injected into the vsense and vinac pins in order to get the chip sending gate pulses....just says above 0.7V.

--- Updated ---

.......UCC28070A is rated for 20mA abs max supply current, so it looks like mine is fried...i used full ESD protection throughout. I am wondering if the chip shortage is meaning almost_empty reels of components are being re-reeled, and this done without ESD precautions.
--- Updated ---

Has anyone noticed dodgy chips, possible from re-reeling-without-ESD-precautions.
In a recent other job a load of control chips were wadgered.
--- Updated ---

Eagle Pro layout and scem attached


  • PFC layout
    48.3 KB · Views: 90
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I am just wondering now......i soldered this board up with an Eagle YO61 solder station......the solder tip is earthed only if the cylinder screw is tight.......i did notice during soldering, that the cylinder screw had loosened right off, and then there's no earth connection to the solder maybe that could have ESD blitzed the UCC28070A?.......What would you think the likelihood of ESD damaging a UCC28070A with a non earthed solder tip? I did have to drag solder the UCC28070A.

If it is ESD damage, then i wonder how the CD74HC123M didnt get ESD damaged (the second one i used)...but then again, it is a 1.27mm chip ...i am convinced that these tiny <=0.65mm pitch chips are more susceptible to ESD damage?
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UCC28070A fact the whole control board was re-built...and all is well now...this looks like an ESD damaged UCC28070A....perhaps damaged in all the re-reeling of chips thats going on due to the worldwide chip shortage?

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