68.6.6.2.1 Application Example

The external PWM Start mode generates a modulated frequency PWM signal with a constant active level duration (t_ON) and a minimum inactive level duration (minimum t_OFF).

The t_ON time is defined by the CDTY value in the PWM Channel Duty Cycle Register. The minimum t_OFF time is defined by CDTY - CPRD (PWM Channel Period Register). This mode can be useful in Buck DC/DC Converter applications.

When the output voltage V_OUT is above a specific threshold (Vref), the PWM inactive level is maintained as long as V_OUT remains above this threshold. If V_OUT is below this specific threshold, this mode ensures a minimum t_OFF time required for MOSFET driving (see the figure below).