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UCC256302: Time to detect dV / dt of UCC256302

user6362776
Prodigy 10 points
Part Number: UCC256302
Other Parts Discussed in Thread: UCC256402

Hello,

I have a question about the detectable slew rate of dVHS / dt.
The slew rate recognizes that 1V / ns ~ 50V / ns must be detected when Vds< 50V.
①Is there a minimum time required for slew rate detection?
②Will the threshold of Vds <50V fluctuate?

Best Regards,

  • 0
    TI__Mastermind 26445 points

    Hello,

    There is not a minimum time to detect the 1V/ns criteria. The detectable range does not fluctuate.

    I would like to mention the newer UCC256402 has a much lower detectable range of 0.1V/ns. The UCC256402 would be better equipped to avoid slew rate detection issues if this is what you are seeing. Some other things that can help with slew rate detection reliability:

    1. increase the turn-off speed of the MOSFETs - this can help increase the slew rate of the switch node

    2. increase the burst threshold - slew rate issues tend to happen at higher frequency/lighter loads. Increasing the burst threshold will make the LLC burst with slightly more power within the burst packet and the resonant current amplitude will be higher. This increases the slew rate of the switch node as well

    3. Lowering the Lm of the transformer will increase the magnetizing current and will help increase the switch node slew rate

    Best Regards,

    Ben Lough