Hello,
We plan to use the DRV8332 driver chip to drive a BLDC hub motor. Here is our current motor controller schematic.
We have little experience with brushless motors, and have run into a couple of issues.
1. When testing the outputs of our PCB (without connecting a motor), we used a voltage divider circuit to supply the following logic signals:
(3.3V Logic)
PwmA,B,C = HIGH, LOW, LOW;
~(ResetA,B,C) = HIGH, HIGH, LOW;
Those values come from S1 of the sensored control timing diagram for the DRV8332 at 100% duty cycle.
We achieved output levels of (roughly)
MotorA,B,C = 0.6 V, 0.6 V, 10.5 V;
This did not match the diagram. Upon further testing, we found that the PWM signals were no longer outputting 3.3 V once they were connected to the PCB.
The reset signals did not cause this to happen, but the PWMs dragged the voltage down to 0.8 V rather than 3.3V.
Do you know what may be causing this?
2. A more general question; What is the preferred method to keep the logic and power grounds from interfering with one another while holding a common reference.
We currently have separate ground planes on our board for logic and power, but connect them at the output terminal. Is this how it's normally done?
Thank you, and any general suggestions or considerations you may have for us are more than welcome.
Sincerely,
Spencer Faull and the Trine University Shell Eco Marathon Team
