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TPS40210 Switch Mode

Stephen Allen
Prodigy 110 points
Other Parts Discussed in Thread: TPS40210

What are the various switch modes for the TPS4010 Gate Drive, and how do I ensure that the TPS40210 stays in a specific mode?  Currently, the desired effect is a Burst Mode with a fixed frequency (35 kHz) and pulse width (~100 ns), however, my circuit/layout is producing a Gate Drive output that is a sequence of short pulses followed by a short "dead time" followed by a single pulse with long duration (source of my ripple).

Thanks.

-Steve

  • 0
    TI__Mastermind 35165 points

    Hi Stephen,

    Sorry for the delay. The images did not post correctly and I bet one of them was the schematic. Can you try to repost this so I can see how you have the TPS40210 configured?

    Best Regards,
    Anthony

  • 0 in reply to Stephen Allen
    TI__Mastermind 35165 points

    Hi Stephen,

    Thanks for sharing the files. There are two things which may be happening.

    First the noise when turning on the MOSFET may be causing a peak in the ISNS voltage causing the the switching cycle to terminate at the minimum on-time. This would cause a series of short pulses and a long pulse which average out to the expected on-time. To improve this, you can try:

    1. Improve the filtering to the ISNS pin and make sure the capacitor is well placed to reduce noise pick up.
    2. Add some series resistance to the gate of the MOSFET to slow its turn on.

    Second it may be occuring because of how operating at the minimum on-time in pulse skipping mode typically works. Pulse skipping occurs when COMP discharges below the valley voltage. This causes the output to decay. In response the COMP voltage will charge up to keep the output voltage in regulation. It may overshoot resulting in the first pulse being a longer on-time. If this is what is happening, you can try slowing down the loop to reduce the overshoot on COMP. This would be done by a combination of smaller R134, larger C121 and larger C119.

    Best Regards,
    Anthony