DRV8871: Start-up current is too large

Hey Allen,

Have they tried with the potentiometer turned all the way to its lowest resistance setting?  According to 7.4.2 PWM Without Current Regulation in the datasheet, this will get near the without current regulation setting.  Alternatively, do as the screenshot says and put a resistor in R6.  Since the peak current of 4.2A is more than 3.7A it might still trigger OCP, but 6.5 Electrical Characteristics gives a range of 3.7 - 6.4A for IOCP so depending on the time it might not.  

Beyond that, I don't see any way to change the t_OCP for this trip or set I_OCP any higher.  

I recommend looking at the DRV8256.  It has a peak output current of 8A, and has current regulation, integrated current sensing, and smart tune.  (EVM)

Another to look at is the DRV8251A.  It has a peak output current of 4.1A.

Cheers,

Jacob Thompson.

hi Jacob:

 tks for your comments. just double confirm and cowork with customer , the Iocp current is up to 4A ,but the hold time is only remain 1us, which < Overcurrent deglitch time(1.5us), so the cycle by cycle function is not working. 

 Do you have another recommendation as below requirements?

 1)  36Vin

 2)  5A ocp roughly

 3)  IN1 /IN2 control

 4)  Brake; fast decay

Hey Allen,

Given those specs I recommend the DRV8256.  Here's a link to the PWM version of the EVM.    

Cheers, 

Jacob Thompson

Allen,

How much capacitance is across the motor?  This fast rise is typically due to capacitance on the motor I = C x dV/dt.  You can isolate this capacitance with a series 5-10uH inductor as a test if this is the issue or not.

Regards,

Ryan

hi Ryan:

 tks for your suggestion! we will check with your solution with the first onboard sample in next week.