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DRV10983: PWM cannot adjust motor speed

Annie Liu
Genius 10295 points
Part Number: DRV10983

Hi Team,

#define REG_20 0x39
#define REG_21 0x38 
#define REG_22 0xAA
#define REG_23 0x08
#define REG_24 0x08 
#define REG_25 0xFD
#define REG_26 0x8B
#define REG_27 0xFC
#define REG_28 0x98
#define REG_29 0x77
#define REG_2A 0x05
#define REG_2B 0x02

The register configuration is as above. No matter how big the input PWM duty cycle is, the motor will always keep running at the highest speed. 

Writing 0X01 and 0X00 registers also cannot adjust the speed.

Reading 0X1E is always 0, no error reported. The value of 0X1B is consistent with the input PWM duty cycle. ReadING 0x20~0x2B, the register value is consistent with the written value.

Customer would like to know how to configure to adjust the motor speed?

Regards,

Annie

  • 0
    TI__Mastermind 24415 points

    Hi Annie,

    Looks like the speed command is buffering. To confirm this, can you read register 0x1C. It should read back a value higher than the speed command (reg: 0x1B). This can happen when the mechanical and inductive AVS is enabled (more details in section 8.4.8 in the datasheet). I see that both are enabled. Can you disable both and try again? Ideally, we shouldn't be seeing this issue if the programmed Kt is accurate. Did you measure the Kt of the motor?

    Regards,

    Vishnu

  • 0 in reply to Vishnu Balaraj
    TI__Genius 10295 points

    Hi Vishnu,

    Disabling mechanical and inductive AVS or adjusting the Kt value can solve this problem. But it will still report kt error at low speed. Customer wants to know how to measure the kt of the motor will be more accurate? The registers have been set to 2kt and 1/2kt.

    Regards,

    Annie

  • +1 in reply to Annie Liu
    TI__Mastermind 24415 points

    Refer to the below image to measure Kt. After measuring the Kt, program this value in the EEPROM and tune the lead time such that the estimated Kt (read back from register address 0x15 and 0x16) stays non zero. If you see Abnormal Kt fault getting triggered while the estimated Kt is non-zero, you can disable the abnormal Kt fault. 

    Regards,

    Vishnu