DRV8323R: Isolator in between MCU and DRV8323R for INHx and INLx

Hi

I am using Isolator to DRV8323 6X PWM Input INHx and INLx pins for isolate driver part with different power domain. I observed that there is 8ns delay between input and output pins and rise/fall time same as controller output.

The motor without isolator is running perfectly , with iso there are distortion in motor commutation, cause of that FETs are taking high amount of current to rotate the motor. there is no fault flag i can read from fault registers.

What could be the reason to not following the same commutation to the output ?  

Isolator Specification  :

Output Rise/Fall Time - tR/tF 2.5 ns

Typical SWITCHING SPECIFICATIONS -

            Pulse Width PW 6.6 ns

            Data Rate 150 Mbps Max

            Propagation Delay tPHL, tPLH  8.7 ns

Sourcing Current - 4.4 mA @ 1 Mbps