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DRV8706-Q1: DRV8706H: I need bidirectional current sensing

Craig Kessler
Prodigy 30 points
Part Number: DRV8706-Q1

I have built a motor controller board prototype using the DRV8706H part.  The product is functioning properly except for the fact that I am only getting current reading in the forward direction. I need to be able to read current in both directions. 

  • MODE:              PH/EN H-Bridge Control - Level 3 (47k ohm to GND)
  • GAIN:                40                                         - Level 3 (Open)
  • VDS :                 Disabled                            - Level 6 (DVDD)
  • IDRIVE:              62mA                                 - Level 6 (DVDD)
  • nHIZ1/nHIZ2:    Disabled                           - Tied to GND

I have a microcontroller reading the SO pin and I get readings in the forward direction only.

Is it capable of bidirectional current reading and if so what I am doing wrong? Thanks for you help!

  • 0
    TI__Mastermind 18505 points

    Hello Craig, 

    I have a few questions:

    Where did you place the shunt resistor?

    what is your V_AREF value and the shunt resistor value?

    Are you reading zero in the reverse direction or is the value that you are reading the same value as the forward direction?

    The CSA_DIV and CSA_SH_EN should both be by default 0b but can you double check that configuration.

    Best,

    Keerthi Kumanan

  • 0 in reply to Keerthivasan Kumanan
    Prodigy 30 points

    I have the hardware version of the chip so register settings don't apply. 

    To the point:  I had V_AREF decoupled but missed connecting to an actual voltage reference in my schematic.  Added a jumper on my prototype board and it is working now.  What do you know, voltage references are important! ;-)

    Thank you for your assistance.