TPS51216-EP supports D-CAP mode which does not require complex external compensation networks and is suitable for designs with small external components counts. The D-CAP mode provides fast transient response with appropriate amount of equivalent series resistance (ESR) on the output capacitors. An adaptive on-time control scheme is used to achieve pseudo-constant frequency. The TPS51216-EP adjusts the on-time (t_ON) to be inversely proportional to the input voltage (V_IN) and proportional to the output voltage (V_DDQ). This makes a switching frequency fairy constant over the variation of input voltage at the steady state condition.