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Original question:

UCC28070: current share test

UCC28070: multiple phase operation

shuang qiu
Prodigy 190 points
Part Number: UCC28070

Hi,

I want to know more details about multiple phase operation.

1. I cannot find current share pin of UCC28070, please advise how the current share work in detals.

2. For SS, IMO pin, if shorted them together, how to set the resistor/capacitor values, is it same as single module setting, or need double or half value?

3. For VSENSE, VINAC, SS, and VAO pins, if using same setting resisstor/capcitor value individually on these pins, but not short the pins together, what will happen?

4. Is there any pin can show current(input or output) value, or equivalent value?

5. Do you have multi-phase test report? any multi-phase demo board available?

Thanks!

  • 0
    TI__Mastermind 31580 points
    Hi Shuang,

    Answers are as follows.

    1. The current share performance is dependent on the relatives tolerance and offsets of the internal amplifiers and comparators of the two UCC28070 controllers, since they are using the IMO signal to measure the current signal for their current loop.

    2. Each controller should be taking 50% of the power so for a 1200W design I would calculate each controller based on a 600W design with say 20% margin to allow for component derating and some mismatch in current sharing during operation.

    3. There will be some additional mismatch between load sharing due to the tolerance of the separate resistive sense chains. I suggest that only one resistive sense chain for VSENSE be used for both controllers.

    4. The current sense only uses the PFC switch current and the controller emulates the downslope internally. There is not complete picture of the input or output current available from the controller.

    5. TI only has the basic schematic in the datasheet. there is no test report of demo board available for multi-phase PFC using the UCC28070.

    Regards

    Peter