Hello
My customer needs some help on the current limit for the DRV8837. Here is the problem description
We are using the DRV8837 to drive motors +/-1 Amp average with a 9V power supply (6 AA batteries) in production. There is 8" of wire between the driver and the motor.
We use caps across the motors to prevent EMI. We use a 0.1uf across the motor leads and two 0.1uf from each lead to the motor case. Electrically it looks like 0.15uf across the DRV output.
We found a problem because the DRV8837 is going into cycle-by-cycle peak current limit even with low average motor current (<0.5A).
We found that the peak current spec is exceeded with the three 0.1uf caps, but also with three 0.01uf caps, and even with no caps.
I'm attaching scope shots of those three measurements.
We want to drill down and find out a safe operating region where we know the limit will not fire. The length of time of the spike must play a roll, but we don't know what it is.
Can you please help us understand where the limits are and how the spike width affects it?
The scope traces are 1A/div. 0.1uf, 0.01uf, and no caps.
Thanks
Faizul Bacchus
