DRV8876-Q1: Current limit when operating in Independent Half-Bridge mode

Hi Jessica,

Thank you for posting in this forum.

Jessica Riley said:

Is it possible to set the current limit while operating in Independent Half-Bridge mode (PMODE = open)?  

You are correct. Internally current regulation is disabled in this PMODE.

Jessica Riley said:

Ideally I would like to operate the device in independent Half-Bridge mode with a maximum output current limit set to 100mA (the actual current will be < 10mA).   Is that possible with this device?

If you could somehow use PWM mode, PMODE = logic HIGH you could use the internal current regulation. By choosing appropriate VREF input voltage and RIPROPI you can set the desired Itrip level. For very low target current fixed TOFF current chopping would be suitable. While 100 mA seems practical for this device while still on the low side compared to its full-scale capability, < 10 mA may have severe SNR limitations and accuracy issues. You may have to characterize and see if it works for you. 

Could you please provide details about the end application requirements, type of load, its R and L characteristics etc., ?  Thanks.

Regards, Murugavel 

I have another open thread here with my application requirements: https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1459525/drv8872-q1-dual-independent-pwm-outputs

- Operating voltage: 7V to 35V
- Output current < 10mA
- Frequency up to 100kHz
- 0% to 100% duty cycle
- Dual channel (independent) preferred for space considerations
- Automotive + functional safety

I want to take advantage of the two independent PWM outputs. 



When in PMODE=HiZ, what happens if the output signal is shorted?  Does it limit to 3.5A? 



Since current regulation is not available in PMODE=HiZ mode, and I don't need current sensing, is it okay to connect IMODE=IPROPI=VREF=GND?

Hi Jessica,

Thanks for the link, I'll review it later and get back with my comments.

Jessica Riley said:

When in PMODE=HiZ, what happens if the output signal is shorted?  Does it limit to 3.5A?

There is an analog current limit protection as described in the datasheet. Let me check if this would be 3.5 A or a different value and get back to you. Thanks.

Regards, Murugavel 

Can you confirm the schematics are okay for the following?

- Independent Half-Bridge mode

- No internal current regulation

- No current sensing

Thank you Murugavel,

The 4.7k pull-down resistors were added because they helped improve the falling edge transition on another driver circuit based on the DRV8703-Q1.  Since we are using the circuit for PWM signals (not driving a motor), the goal is to keep the edge transitions as sharp as possible.

We will add the optional resistor loads per your suggestion.