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DRV8412 output issues at low duty cycles

Anthony
Prodigy 30 points
Other Parts Discussed in Thread: DRV8412

Hello,

I am using the DRV8412 in parallel full bridge mode as a bipolar drive for a peltier unit, using two complimentary PWM signals at 250kHz. The circuit has an LC filter on the output, as well as some smaller inductors to prevent shoot-through current.

I've been debugging the the circuit using a 5 Ohm resistor, and GVDD of 24V. Looking at the output of the DRV8412 at different duty cycles, I'm seeing one of the synch'd half-bridges start doing strange things at duty cycles less than 25%. Note that I don't see this happening at duty cycles above 75%, which is strange as the output circuit is symmetrical.

Note I've checked the input signals, and they are complimentary and as expected. When I remove the load resistor, the signal is restored to normal.

Any feedback would be much appreciated as we have several projects which are looking at using Peltier units, and this IC was the perfect candidate until I came across this issue.

Thanks,

Anthony

  • 0
    TI__Guru** 114905 points

    Hi Anthony,

    Can you provide more information? What are channel 1 and 2 of the scope shots?  Is there any additional components/circuitry hanging on channel 2 vs channel 1?

    Can you provide a scope shot with one of the two PWM inputs for time reference?

    Are you using the TIEVM or your own design? If your own, can you provide the schematic and layout?

    Thanks.