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# DRV11873EVM - Motor stops over 9500rpm

Other Parts Discussed in Thread: DRV11873EVM, DRV11873

Hi Team,

Our customer is evaluating the device using the DRV11873EVM.

They want to use the device to control the motor at 10000rpm, but the motor always stops at around 9500rpm.

What is the problem ? Is there anything that limits motor speed ? LS pin setting ?

[Customer Condition]
- Motor type : Star wiring motor
- have no changes on the EVM
- They tried changing VCC or PWM frequency, but no change.
- Load current at 9500rpm is 100mA, 150mA(peak), not in current limit.

Best Regards,
Kawai

• Hi Kawai

Could you give the pole pair (PP) numbers of your motor? Based on RPM = 60*FG/PP. We need to know the MAX FG when it at 9500rpm.

DRV11873 has a fixed MAX speed limit of the internal control logic. The limit is FG < 475Hz@FS=0 and 950Hz@FS=1 .

Besides calculate the FG, you can directly measure the FG signal from the FG pin (with pull up to VCC or V5). If it is true reached the limit. We can do litte about it other than lower down the speed.

Thanks,

Wilson Zuo

Motor Application Team

• Hi Wilson-san,

The Pole Pair (PP) is "6", calculating FG = RPM * PP / 60 = 1000Hz@10000RPM.

I understood that this is over the limit of device control logic.

To achieve 10000RPM, maybe you may need to choose motor witch has lower pole pair numbers.

Best Regards,
Kawai

• Hi Kawai

Yes. Motor with lower pole pair numbers usually comes with lower FG and higher RPM.

Thanks.

Wilson Zuo