Hi,
I have implemented a Parallel Full bridge with DRV8412 to drive a Brushed DC Motor. I have used an NXP8951RD2 microcontroller for controlling this. My nominal supply voltage to the Motor driver is 28VDC (motor). The RD2 runs on 5V. I have used a level translator in between the driver and the microcontroller to convert 5V to 3.3V level signals. However the PWM output pins of the RD2 have a internal weak pullup. So when the PWM is disabled, the lines go to high.
Our observations:
1. At power ON we are applying a reset pulse, the outputs of the driver remain floating at 10V.
2. However after the 1st PWM pulse train is applied on one side (one direction), the other line goes low (even when that particular input is high), and the pulses follow the input.
3. As soon as the pulse train is stopped and both the inputs go high, then most of the time, both the outputs remain low, but sometimes, the output on which the Pulse train was applied earlier - goes high.
4. This is causing the motor to rotate at full speed.
We have demonstrated this issue to the Local TI support. They have reviewed our schematics and layout and were not able to find anything wrong in our implementation. They asked us to check the same with an DRV8412 EVM. Today, we did this same experiment with the EVM and found that the behavior is the same as we have observed earlier.
Please let me know whom do I send our detailed observations, schematics and waveforms which show this problem. We need to resolve this issue at the earliest.
Kindly reply back at the earliest.
Regards,
Ravindra Munvar
Philips India Ltd. Pune Mob: +91-9766224400
e-Mail: ravindra.munvar@philips.com
