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DRV8701: Questions regarding the motor driver DRV8701, control method

Yiming QIAN
Prodigy 15 points
Part Number: DRV8701

I'm using the DRV8701P to build a bridge control for a Brushed DC Motor. I would like to know below points regarding the driver DRV8701.

1)  What is the purpose for SNSOUT, if I control the driver and motor by PWM, shall I still use the pin of SNSOUT?

2) What condition will cause a nFault signal?

3) How to deal with the nFault signal, shall it vanish after a reset or power off? How to clear it?

thanks!

  • 0
    TI__Expert 4970 points

    Hello Yiming QIAN, 

    I will be happy to help out with your questions. 

    1. SNSOUT is part of the current regulation system that allows you to set a max current threshold through the motor. For DC motors, current regulation is generally used to limit the start-up and stall current to the motor. It is generally a good idea to have said protection, Page 16 of the datasheet explains in detail how to set up the current regulation system and the equations necessary to hook it up correctly. However if you would like to avoid the current regulation system altogether and depend on the fixed off time of PWM to regulate current then you can do so by: tying VREF directly to AVDD and tying SP and SN to GND while implementing a pull up resistor for SNSOUT.

    2. There are many different conditions that can cause an nFault signal: VM under voltage lockout, VCP under voltage lockout, overcurrent protection, thermal shutdown, pre-driver fault, etc. 

    3. In order to know how to restore it you will need to identify what, of the many different possible causes, was the culprit for the nFault signal. However helpfully the documentation states what will happen in each result such that you can determine how to fix it. Page 24 of the documentation goes into great detail on how to identify the different fault conditions. For example, the VM under voltage lockout will have resumed operations and the nFault signal released when the voltage rises above the UVLO threshold.

    Please let me know if you have any other questions and thank you for your inquiry. 

    Best,

    Pedro Arango Ramirez