DRV 8834 behavior on nENBL pin high and low state

Hi,

I have a query regarding the DRV 8834 driver. We are using DRV8834 to drive stepper motors.

The motor interface document is attached for your reference.

The application is driving 6 motors through 6 DRV8834 drivers one at a time.

The STEP, Dir are common which go to all 6 DRV8834 drivers.

Only the enable pin of DRV8834 is selected by a MUX to enable the specific DRV8834 to drive respective motor.

The following configuration is used

Controller used to drive DRV 8834 driver      :              LPC1788

STEP size                                                              :               1/16 set through the controller

Direction                                                              :               Forward/Reverse set through the controller

PWM frequency for STEP                                  :               250 Hz set through the controller                                                                                             

Flowing are the steps to drive the stepper motor through DRV8834 driver

1. Set Backward Direction

2. Enable the DRV 8834 output by driving the nENBL pin low

3. Wait for 500 ms

4. Start PWM at 250 Hz frequency

5. Stop PWM pulses and then motor by driving the DRV 8834 nENBL pin high

6. Set Forward Direction

7. Enable the DRV 8834 output by driving the nENBL pin low

8. Wait for 500 ms

9. Start PWM at 250 Hz frequency

10. Wait for fixed no of pulses to complete

11. Stop PWM pulses and then motor by driving DRV 8834 nENBL pin high

12. Go to step 1 and then step 2 to enable next DRV 8834

Observations

1. When DRV 8834 nENBL pin is driven high to stop the motor and again enabled when switching to next motor a small jerk is observed on the output mechanical assembly which is connected to next motor. This jerk is observed on all motors connected to respective DRV 8834 drivers. This jerk is observed exactly when DRV8834 nENBL pin becomes low and no PWM pulses are started at this point.

    

Query

1. In our application we have to control 6 motors one by one and due to this jerk we cannot control the motor position accurately.

How to eliminate this initial jerk?

Thanks and Regards,

Anuj Tanksali