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UCC2897A: PMP5124 EVM spike issue

Tommy Tzeng
Mastermind 6400 points

Part Number: UCC2897A

Hi Sir,

we test the switch phase and found the spike to be very high on PMP5124 EVM board, is there any way to improve? or have any suggestiom for us?

After our checked the PMP5124 EVM, and then found the same issue with (Q3) VDS over MOS spec (>150V) during Power off mode,

    PMP5124 Test result as below,

     Test 1

     CH1 PWM mosfet (Q3) Vds

     CH2 Vi

     Test condition 12V/0A (at light load)

Test 2

CH1 PWM mosfet (Q3) Vds

      CH2 Vi

      Test condition 12V/7A (at full load)

  • 0
    TI__Guru 74075 points

    Hi,

    Power off through Vin LineUV off with self-driven SR would have such voltage spikes at the switch node. A typical way is to make the soft stop time longer. To do this, the IC VDD needs keep above its UVLO off, then increase the soft start capacitor value.

    Add some additional dummy load to the secondary side.

    Use controlled driven SR.