questions on using InstaSpin BLDC & DRV8313 for a new sensor less BLDC motor design

Hi,

  We are using DRV8313 for a new sensor-less BLDC motor with instaspin software on MSP430.

  In our design, we use OPA337, instead of OPA365 (used in DRV8313EVM), for IDC_SENSE feedback.

  1. When we connect DRV8313EVM to our BLDC motor, everything seems to work.

  2. When we connect our own PCBA (with OPA337), the motor will spin and stall for 5-10 seconds.  And then an error is shown as "hardware no connection."  When I say "spin and stall", the motor seems to rotate for about 120 degrees and then stop.  Then, it rotate another 120 degrees and stop again.

  I would like to know if this problem is related to a different OP is being used.  If so, can we change something in InstaSpin to adjust for the new OP?  

  Any suggestion will be appreciated.