Register settings in TI motor drivers allow you to configure specific settings to optimize motor driver performance for your particular application. Whether it is adjustable IDRIVE, dead time, or setting the overcurrent trip threshold, register settings are key for allowing you to operate the motor in a way that best fits your needs. But when is it necessary to configure the registers? After initially powering on the device, shouldn’t you be set to configure them once and then never have to think about them again?
Not Quite. There are a few additional conditions that need to be considered. For motor drivers with volatile memory, the registers will be reset to their default values any time the digital circuitry does not have sufficient power. This could occur during an undervoltage condition or due to putting the device into sleep mode.
Reconfiguring your motor driver’s register settings after exiting sleep mode
When a device enters sleep mode (which can be done through pulling the nSLEEP pin or the ENABLE pin low depending on the device), the driver enters a low power state to significantly reduce power consumption while the driver is not in use. In order to achieve this low power state, the internal voltage regulators of the device are shut down. As a result, the digital core will be shut down and the register settings will be cleared. When the device is reenabled, the registers will power up with the default register settings of the device.
It is important that the MCU reconfigures the desired register settings of the driver over SPI after exiting sleep mode. Failure to do so can result in operating the driver in a way that is not optimized for your system, and in some cases can lead to damage such as when too high of an IDRIVE value is used for your system.
Reconfiguring your motor driver’s register settings after an Undervoltage fault
When a device experiences an undervoltage fault, this can result in the voltage of the internal regulators dropping too low, causing the digital core to reset. Once the device recovers from an undervoltage event, the registers will be initialized to their default settings. As a result, it is important that the MCU reconfigures the desired register settings of the driver over SPI after recovering from an undervoltage event. Failure to do so will result in operating the motor with incorrect driver settings for your system.
If you are unsure if your register settings have been cleared, you can perform a SPI read of a register where you have configured settings different from the default settings. If the readback indicates that the register settings have been changed from what you have written, then that is an indicator that you need to rewrite your register settings. It is also a good practice to read back the register settings after writing them to make sure that all the registers were properly set to the desired values.
