A second order charge pump (SOCP) scheme is proposed in this letter. Compared with the conventional single charge pump, the second order charge pump does not suffer phase errors caused by the output voltage dependent current mismatches. Also, the second order charge pump can be implemented in a mixed-mode type, enabling the fast lock and the various operation modes simultaneously. The proposed SOCP has been adopted into the duty cycle corrector (DCC) loops of DDR2 DRAM, and shows a much widened correction range owing to the removal of the parasitic effects.