Tool/software:
Hi team,
My customer Valeo asked that Aout/Bout of the DRV8889 is driven by H bridge so the output voltage( A1-A2) should be either close to +/-VM(high side mos+another low side ON) or close to gnd(both low side mos ON).
But they find in the test that when output current close to 0, The output voltage is 6V. How to understand this phenomenon? Is there any risk? VM is about 12.5V in their project.
Best Regards,
Xiaowei Zhang
Hi Xiaowei,
My customer Valeo asked that Aout/Bout of the DRV8889 is driven by H bridge so the output voltage( A1-A2) should be either close to +/-VM(high side mos+another low side ON) or close to gnd(both low side mos ON).
But they find in the test that when output current close to 0, The output voltage is 6V. How to understand this phenomenon? Is there any risk? VM is about 12.5V in their project.
This is expected behavior, no risk in operation. See this below capture with VM = 12 V. Purple trace is the coil current and yellow trace is voltage AOUT1 and AOUT2. During the STEP where coil current is 0, the full-bridge for coil A, AOUT1 and AOUT2 will be Hi-Z. The mid-level analog voltage observed during this time is the VBEMF of the stepper motor. Depending on the motor L and R and construction as well as motor speed this level may vary. Also you can notice a voltage pulse in opposite polarity occasionally. These are due to fast-decay activity when the current is decreasing. Thank you.
Regards, Murugavel
