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DRV8432 hidden output short
I recently made some test boards to get the DRV8432 running for our application, but I'm experiencing high currents with no load when I apply a PWM signal. See schematic below:
Not shown in the above diagram is large bypass caps for the PVDDs (I will eventually be driving very inductive loads). There's also regulators for GVDDs to keep them at 12V.
I have a power supply connected to the circuit, current limited to 2A @ 17V. When I apply a PWM signal, the current hits maximum and the voltage drops to around 11V, the DRV832 starts heating up (I had removed the heatsink to feel for heat). I have tried removing U21 and U26 incase these chips where causing problems, but this did not make a difference. I can't find any shorts. I have two boards made, and they both behave the same way which makes me think I may have missed something in the design.
The PWM signals I'm sending are either complementary or all low. The high current does not occur when all PWM signals are low, it only happens when I apply a PWM signal. The fault pin does not go high, but I'm sure OTW will eventually if I keep the thing running.
I'm going to try removing those caps that shouldn't really be there (C59,C61, C71, C72, they should have been connected to the PVDDs, but I can't image this causing the problem)
I can't think of anything else that could be causing the high current through the DRVs except for faulty chips, but what are the chances of two faulty chips? hmmm....
PWM Frequency is around 250Khz, and I'm only doing 50% for now, so boot-straps should be functioning fine.
Can anybody see something I may have missed? Or possible things I could try to debug this?
Nevermind, it totally was those caps I put in the wrong place. I guess their impedance was low enough to cause that "short".
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