A 6-bit self-clocked tracking ADC for the application in DC-DC converters is presented. Depending on the characteristics of the input signal, the adaptive control mechanism automatically increases or decreases the self-clocked frequency to match the tracking and energy efficiency. The ADC described in this paper has a high conversion rate of up to 50 MS/s with 2.6 pJ/conversion-step. The prototype ADC occupies a very small chip area of 400×200 μm² on a 130 nm 6M1P technology. Without using costly amplifiers, the maximum power dissipation is 84 μW at a supply voltage of 1.4 V when operated at 50 MS/s.