DRV8876EVM: DRV8876EVM

Hello Ho,

Thank you for your post.

Ho yulung said:

If the motor current is running under normal settings and then suddenly gets stuck, causing the current to increase abnormally, how can we control the external PWM voltage to immediately reduce the current to the limited current value?
For example: set the current limit value to 0.5 A and the operating voltage value to 12V. After the motor is connected, the motor's operating current is 0.2A. Ten seconds later, the motor gets stuck and the current suddenly rises to 3A. How can I reduce 3A to the set 0.5A?

There are two ways you could achieve this. First approach would be to use the on-chip current regulation. See below from the datasheet. VREF and RIPROPI must be set according to your requirements, 0.5 A like you mentioned and the formula shown. For low current amplitudes "Fixed off-Time" current chopping would be better. With VREF = 2.5 V, RIPROPI would be 5 kΩ for ITRIP = 0.5 A. Note, this also would affect the motor startup because the inrush current also would be regulated to 0.5 A which means the motor will accelerate slowly to steady state speed. You must ensure the motor is able to overcome load inertia with 0.5 A ITRIP setting. 

The second approach would be to set VREF voltage to its highest value 3.3 V maybe and size the RIPROPI such that it will not reach 3.3 V even with 3 or 5 A motor current. This will ensure internal current regulation would not kick-in. You can connect the IPROPI / RIPROPI to external MCU ADC input and sample it at the desired sample rate. Based on the current value read by the ADC you can reduce the PWM duty cycle to reduce the average current. Using the first approach would be the simplest and is an available feature of this device. Thank you.

Regards, Murugavel