Techniques and apparatuses are provided for determining the efficiency of a charge pump. A charge pump is driven during a measurement period without limiting its input current. The driving can include ramping up the output of the charge pump from an initial level to a final level and maintaining the output at the final level. A counter counts a number of clock pulses provided to the charge pump during the measurement period. Using a current mirror which limits the input current, a ratio of the current mirror is determined which results in a similar number of clock pulses during the measurement period. The ratio indicates an efficiency of the charge pump and can be used to set control parameters such as ramp up rate and clock frequency.