DRV10975: DRV10975 SPEED CONTROL ISSUES

Part Number: DRV10975

Dear  TI Guys:
   
      I use drv10975 for Air-condition Drain pump. Motor parameters as follow:
1. rated voltage:12v
2. rated current:0.4A ; Peak current:1A
3. Max speed; 4500rpm(no-load)   3000rpm(load)
4. Phase Resistance: 5.17 ohm
5.Kt = 43~54mV/HZ;
6. #polo= 8  
     

I use Drv10975evm to drive the motor, it can spin  but the speed only 300 rpm, i can't the improve the turn speed. and the Peak current can reach 2A (Too high)
Turn the pot to max value, test speed pin value is 3.2V. the speed also 300 rpm.
there maybe sth wrong in the parameter setting, can you help me?
thanks a lot