Hi,
We have some troubles with DRV8323 analog path. There is BLDC controller board with DRV in each of two channels. We have tested one channel driving power stage to a constant duty cycle that lead to ~40A current trough the load. Voltage drop across the low side current shunt meets expectation (square waveform), ut output. But output signal from DRVs current sense amplifier was dirty and useless.
What we did:
1) Cut SNx pins from common ground plane and connect them to current shunts directly (by wires);
2) Removed output filters on SOx pins;
3) Removed decoupling capacitors on FETs (C56, C57, C58 on schematic);
4) Shorted ferrite bead (FB5, FB6) between signal and power ground planes.
But output signal still contains strange long transient. This makes measurements unusable. What could be the reason?
Attached:
1) Picture of PCB layout with measuring points marked (pcb1);
3) Waveform g10 (with 40 gain), blue - shunt voltage drop, yellow - SOx pin;
3) Waveform g11 (with 5 gain).
