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DRV421: DRV421 Field Direction and ICOMP Polarity

Paul Gyurkikiss
Prodigy 10 points
Part Number: DRV421

Hello,

I'm trying to implement a closed-loop current sensor using the DRV421.  One problem I have encountered is that neither the data sheet nor any application notes gives the polarity relationship between the magnetic sensor and the compensation current H-bridge.  The data sheet shows the AXIS of magnetic field detection, but not its "polarity".  Or at least, I can't find it.

What I need to know is:  What direction of magnetic flux results in what polarity of compensation current?  I find it strange that it isn't explicitly stated somewhere in the data sheet or an application note.

Any help would be appreciated.

Paul

  • 0
    TI__Mastermind 32260 points

    Paul,

    Thanks you for posting on the E2E forum.  Let me go 2 ways to do this.

    The easiest way and quickest way to determine the correct orientation or connection of the compensation coil is to see if the measurement is saturated then reverse the connection of the ICOMP pins or place the DRV421 oriented 180 degrees to get the opposite field to create the negative feedback required.

    The other way is to observe the top of the DRV421 is an arrow pointing way from pin 1 toward pin 15.  We will call this the positive field.  We will need a negative feedback to this field using our compensation coil.  Think of the current going from ICOMP1 through the coil and Rsense and back through ICOMP2.  This current needs to create a field in the negative direction of the arrow.  Use the right hand rule and determine the direction of the flux based on the core wingdings on the compensation core.  Verify this is creating the negative feedback required.