DRV8323: Adjusting current control gain

Tool/software:

Hello,

We are working on a device design for React Health. I have a question about your DRV gate drivers that I am hoping you can help answer or point me in the direction of someone who could.

Our device design incorporates a 3 phase brushless DC motor for which we would like to use TI's DRV gate driver to drive our motor FETs, use for current sensing, as well as some of the other integrated features of the part. 

We have placed a DRV8323 (DRV8323RHRGZR) on our development board and have our motor running with it. However, we have come upon a question while trying to tune the motor control software for performance that relates to the internal current sense circuitry of the DRV.

A little background...

In a previous design we had utilized the DRV8300 (DRV8300DRGER) and had a discrete current sense solution external to the DRV.

This external circuit gives us a nominal op-amp gain of 5.7 and an actual realized gain of 5.18. About 91% effective with some of the front-end resistor network attenuation. 

We tuned our motor control SW on that design per the effective 5.18 gain and all worked well, peak performance that we needed from our motor.

On our current design,  we would like to use the DRV8323 with the integrated internal current sense circuitry. We have the ICs Gain pin to ground to setup a 5x gain. I am assuming this is the nominal op-amp gain and does not account for any input network attenuation or other loss in the chip?

Can you share what the effective gain is expected to be so we can dial in our tuning and maximize our motor performance? Ideally, what the internal values for the input resistances (R1/R2) and the feedback resistances (R4/R5) are in the design of the DRV8323's current sense? 

Empirically we have found that a 91% effective gain works well, so an effective gain of 4.55, but would like to know if this makes some sense from the internal design of the DRV?

 Let me know if that makes sense and if you or someone can help us answer.

Thanks,

Mike