Other Parts Discussed in Thread: DRV8353
Tool/software:
We are using the DRV8353 in 6xPWM mode. Upon asserting EN = HIGH, the PBLS (Phase B Low-Side Gate) output turns on immediately, even though no input signals (INHx/INLx) are applied — all 6 PWM inputs are confirmed LOW and are disabled.
This issue:
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Happens consistently on multiple boards.
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Persists even after replacing the IC three times.
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Occurs before any switching signal is given.
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Triggers a gate drive fault due to LS FET turning on unintentionally.
Additional observation:
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With no VREF connected, we observe ~2.8 V between gate and source of PBLS the moment EN is high.
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When 5 V VREF is supplied, the PBLS gate voltage jumps to ~7.8 V, again with no PWM input.
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This behavior is specific to Phase B low-side — PHASE A and C behave normally and no fault is shown for other MOSFETs.
- The other phase mosfets can be operated once the fault is disabled, but the voltage of 2.8/7.8 V across gate (GLB) and source (SPB) is still persistant and this is driving the PBLS FET.
We have verified:
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6xPWM.
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INL_B has a pulldown and no signal is applied.
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Bootstrap caps and decoupling are in place.
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No SPI writes are done before the fault occurs.
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VM, VCP, and VGLS voltages are within expected range.