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MCT8316Z: Low speed control current waveform abnormal.

Part Number: MCT8316Z

the pic show, when motor run in low speed, the current waveform is abnormal.

As shown by the red mark ,during the test, the current was cut off.

Is this because of abnormal commutation? Or is it because the current is too small? Do you have any comment on this?

(yellow one is U voltage, Green one is Iout. Blue one is FG signal)

(Motor parameters :15 pole pairs, kV=16rpm/V, phase resistance=0,17Ohm, Phase inductance=0,33mH)

o            PWM frequency : The frequency sent by MSP430, 20kHZ

o            ADVANCE: 0°(R27 = 0 Ω)

o            MODE: Digital Hall Input, Synchronous modulation, ASR and AAR Disabled(R22 = R29 = DNP)

o            SLEW : 25 V/μs (R26 = 0 Ω)

o            ILIM: MCT8316 current limit has not been changed (8A)

  • The issue is that the applied PWM duty cycle is very low. When using a very slow SLEW setting, that results in barely any output from the driver.

    Making SLEW the highest setting improved the duty cycle resolution at low commanded PWMs and allowed the motor to run at 5RPM.