DRV8876: DRV8876 IPROPI Bandwidth

Hi SunSet,

Not sure if this is what you are looking for. From page 10 of the datasheet:

The IPROPI output bandwidth is limited by the sense delay time (tDELAY) of the DRV887x internal current sensing
circuit. This time is the delay from the low-side MOSFET enable command to the IPROPI output being ready. If
the device is alternating between drive and slow-decay (brake) in an H-bridge PWM pattern then the low-side
MOSFET sensing the current is continuously on and the sense delay time has no impact to the IPROPI output.

If you need more information, please provide the conditions you want. We may have to contact the design team.

Hello Rick,

thanks for your feedback, the info I would need is more in frequency perspective.

For instance if I would do the FFT of the current. and before the ADC sampling the current I put a low pass filter, till which frequency make sense to set the cutoff frequency. What is the maximum sampling frequency that really make sense to use for the ADC?

How fast in the time domain can change the current and what would be the maximum frequency that the internal circuitry would allow getting out to the pin Ipropi?

I need to understand how to dimension the signal chain before the ADC and what is the maximum BW that make sense to sample.

I need to implement a control loop based on I and the maximum control loop BW is also related to the maximum I BW.

I hope I clarified the needs better.

Thanks,

SunSet

Hi SunSet,

"For instance if I would do the FFT of the current. and before the ADC sampling the current I put a low pass filter, till which frequency make sense to set the cutoff frequency. What is the maximum sampling frequency that really make sense to use for the ADC?"

This depends on your motor and system.
What is your PWM frequency?
Do you intend to measure the current every PWM cycle?

"How fast in the time domain can change the current and what would be the maximum frequency that the internal circuitry would allow getting out to the pin Ipropi?"

After the blanking time (tblk), the current change follows the load current. If the load is resistive, the current changes quickly. If the load is inductive, the current change is slower.

The IPROPI pin is a current proportional to the output current. The output is typically 1000uA/A.

Hello Rick,

thanks for the input.

I do not have the info on the PWM frequency, but your are right the LR made by the motor will limit the BW.

Knowing a rough number of the BW limit of the chip will help.

We do not need an exact number but  a rough number.

If we do not have any info I can let them test it.

Thanks,

SunSet

Thanks for the confirmation. I would recommend to test it.

Would you recommend any procedure for testing it.

Do we have any literature/whitepaper for it?

Thanks,

SunSet