A circuit includes a microcontroller having a clock output and a data output. The microcontroller includes a serial-peripheral interface (SPI) circuit, a pulse-width modulation (PWM) generator, and a central processing unit (CPU). The SPI circuit is configured to provide an SPI clock signal and an SPI data signal to the data output. The PWM generator is configured to provide a continuous PWM signal to the clock output. The CPU is coupled to the SPI circuit and the PWM generator, and the CPU has executable instructions configured to synchronize the PWM signal to the SPI clock signal.