Part Number: DRV8711
I am using DRV8711 to drive 4 motors on one PCB. When we do run-in mode before functional test. The fault pin active sometimes. We tried to adjustment the software and different PCB layout. But the situation still happens. Can someone help to solve this problem? Many thanks.
In reply to Rick Duncan:
Please refer to the attached file.
DRV8711 MOTOR CURRENT MEASUREMENT.pdfDRV8711 SHUNT RESISTOR VOLTAGE MEASUREMENT.pdf
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In reply to HK2245:
If you still have problem there are some my suggestions
1. Use gate resistor (47 - 100 Ohm) for low side MOSFETS
2. Try to eliminate RC filters for AISENN/AISENP (differential pair from sense resistor to AISENN/AISENP placed over PCB ground layer could be sufficient)
3. Instead of polymer caps decoupling 24V, better choice might be 10-100nF MLCC for each high side MOSFET (placed as close as possible to these mosfets and GND) + 1uF- 2,2uF MLCC for each
H-bridge + single 1000uF - 4700 uF electrolytic cap to store energy from vibrations and breaking.
4. Use 4 layer PCB with 1-2 ground layers if possible.
5. 0,022 - 0,033 Ohm resistor might be a better choice for 4A (less power losses and still good current control)
In reply to Grzegorz Pelikan:
Do you have a current probe? If so, please provide a scope capture of the current through the windings just prior to the nFAULT signal asserting.
This will help provide information on the cause.
If you do not have a current probe, please provide a scope capture of the voltage across the sense resistor to GND prior to nFAULT asserting. This can be more difficult to interpret.
Thank you for the scope captures. Can you answer a few questions about them?
1) What is the scale in the current captures? 10mV = ?A2) Is the motor accelerating (STEP frequency increasing) in the PHASE A and PHASE B image? What is the STEP frequency range?3) When did the fault occur in 2. Motor Current Waveform (Fault pin enabled)4) What fault was reported by the DRV8711?5) What is the STEP frequency in Image 1 of the shunt resistor images?
Has the firmware engineer confirmed the registers writes?
If the motor is not connected, do you get the OCP fault? If so, please check the layout.
Best Regards,Rick DuncanMotor Applications Team
I need more time to do test. Will update later. Thank you for your support.
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