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UCC28C56EVM-066: .

Yadala Tejasri
Prodigy 70 points
Part Number: UCC28C56EVM-066
Other Parts Discussed in Thread: UCC28C56H

Hello,

I am working on UCC28C56EVM-066 Evaluation board for my testing.

My board needs a supply of 5V from Evaluation board. So, I am taking supply from Vaux (18.7V) to my board. My board takes max. current of 100mA.

Since I was checking section by section, things connected on my board is only TPS7B6950QDCYRQ1 Regulator which converts 18.7V to 5V and ATL432LIAQDBZRQ1 shunt regulator which converts 5V to 3.5V.
Before connecting Evaluation board, tested my board from power supply and observed current drawn is max. 21mA and voltages are as expected (5V and 3.5V).

Once my board connected to Evaluation board (Vaux), the Evaluation board stopped working. 

Yesterday when only TPS7B6950QDCYRQ1 is soldered, observed 0mA is drawn when connected to power supply. Then connected to Evaluation board (Vaux), both my board and Evaluation board is working.

So, what is the issue making Evaluation board to go bad, and what is the max. current on Vaux Aux output ?

Please let me know any information is needed and help me out in solving this issue.

Thank you,

Tejasri.

  • 0
    TI__Mastermind 33115 points

    Tejasri,

    I'm sorry but I'm not clear on what you are describing? How about pictures, schematics, block diagram, waveforms to help share the details?

    Regards,

    Steve

  • 0 in reply to Steven Mappus1
    Prodigy 70 points



    UCC28C56EVM-066 Evaluation board | TI.com - Link for Evaluation board which I am talking.

    I need the details of Aux pin - what is the max. output current of Vaux pin.

    And current details on ZD2200-BE transformer.



    Thank you,

    Tejasri.

  • 0 in reply to Yadala Tejasri
    TI__Mastermind 33115 points

    Tejarsi,

    AUX available output current combined with VOUT current is limited by CS (set by R24//R25). VOUT will require most of the total CS current, while the current through AUX will be determined by the current demand coming from VDD (pin 7) of the UCC28C56H. IVDD is the quiescent current, Iq, and the current required to drive the MOSFET Q5. MOSFET average current is, IOUT=Qg*F. The total AUX current is Iq+Qg*F=1.3mA+(13nC*43kHz)=1.86mA. Assume the total AUX current needed for PWM quiescent bias and MOSFET switching is less than 2mA. If you want to steal some AUX current for biasing other circuits, it should be ok up to 1A (the current rating of D12, D13) but I would recommend to limit the AUX current to 10's of mA and be aware that every bit of power taken from the AUX winding is that much less power available for VOUT.

    Regards,

    Steve