ZHCSHA0C January 2018 – September 2018 DRV10974
Assuming the motor used in the application falls within the recommended application range shown in Table 6, the DRV10974 device is simple and intuitive to interface with. The DRV10974 device receives a PWM input that it uses to control the speed of the motor. The duty cycle of the PWM input is used to determine the magnitude of the voltage applied to the motor. The resulting motor speed can be monitored on the FG pin. The FR pin is used to control the direction of rotation for the motor. As a result, the only configuration and customization is dictated by the RMP, ADV, and CS pins.
The resistor on the CS pin is usually determined by the application specifications. Because the CS pin determines the current limit, specifications such as motor current or input power can determine what value the current limit can be set to. Then, the RMP and ADV resistors must be set experimentally through tuning. The RMP pin sets the acceleration profile of the motor. If the RMP pin is set to faster acceleration, the motor starts up faster but may be more likely to fail start-up. In addition, the ADV resistor controls the lead time so the applied current is aligned with the BEMF of the motor. If the ADV resistor is incorrectly selected, the motor may not run efficiently or at all.
As a result, the RMP pin is usually set to the slowest profile while ADV is correctly tuned. Then, the RMP can be set to a different value that allows for a faster acceleration with no impact to start-up reliability. This process, and other design considerations, are documented extensively in the DRV10974 Technical Documents tab on the DRV10974 product page.