This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV425-Q1: Compensation Coil configuration(s)

Part Number: DRV425-Q1

Hello Javier:

Thanks for the help with my prior questions.   

There are three different documents that TI has published with slight variations on the connections of the Driver and the compensation coil

1.In the EVM, the DRV425-Q1 drives the shunt resistance directly with DRV2 and drives the compensation coil oppositely with DRV1 connected to COMP1; the compensation coil (COMP2) is terminated at AINN ( in Figure 6)

2.The data sheet's simplified schematic has the DRV425-Q1 drives the shunt resistance directly with DRV1 and drives the compensation coil with DRV2 connected to COMP2; the compensation coil (COMP1) is terminated at AINN

3. The Bus Bar application note is a further variation but seems to follow the EVM configuration: the DRV425-Q1 connects DRV1 to COMP1 to drive the compensation coil oppositely; COMP2 is terminated at AINN.   This configuration doesn't use a direct drive of the shunt resistor ( in Figure 1)

Sorry for the verbiage... I couldn't figure out how to paste graphics.  I hope I'm just misinterpreting these 3 documents and you can clarify the configuration.

I'd assume that either of the DRV outputs (1 or 2) can drive the shunt and the other output can drive the compensation coil; the coil should be terminated at the AINN input to the 4x diff amp.   Is this correct?  If so, this would mean that the EVM's Figure 6 is the best representation.

Thanks in advance,


  • Frank,

    Thanks for reaching out.  The biggest concern is you need to connect DRV1 to COMP1 and DRV2 to Comp2 (exception is in Dual bus bar configuration)  The placement of the Rshunt is anywhere along that path.  The AINN and AINP will only matter want to change polarity of your Vout measurement.  

    Hopefully this clears it up.  If not let me know.

  • Hey Javier,

    Thanks for the reply but it did spur a follow-up question:  what did you mean by 'change polarity of your Vout measurement.'?

    I am using multiple DRV425-Q1 devices to measure 60 Hz AC current so the polarity is constantly changing.



  • Frank,

    This just means if you are measuring a field in the positive direction it will generate a positive current through the compensation coil.  If you connect the AINN and AINP to the Rshunt in one orientation you will get a voltage at Vout above Vref.  If you reverse the connection to the AINN and AINP from your Rshunt your voltage will now measure a voltage below the Vref voltage.  Measure an AC field will not be and issue.