The TPS929121-Q1 has internal precision oscillator for PWM generators. In addition, the device also supports an external clock for the PWM generator source with ADDR2/CLK input considering the synchronization requirement.

Then external clock inputs through ADDR2/CLK pin is a multi-function pin not only for external clock input but also for device slave address selection. The device slave address stored in EEPROM must be enabled by burning EEP_INTADDR to 1 to release ADDR2/CLK pin for external clock input. In addition, register CONF_EXTCLK can be used to choose the PWM generator between external input or an internal oscillator. Writing CONF_EXTCLK to 1 enables the external clock source. The external clock frequency must be 256 times of desired PWM dimming frequency. The external clock source is only used in PWM generation. TI recommends that the external clock frequency be less than 1 MHz. The internal clock is recommended when high dimming frequency is required.