Spark current in charge pump of phase lock loop

Charge pump is one of the key units in a phase lock loop (PLL) (Gardner, 1980). The operation principle of a charge pump is the current charges to and discharges from a capacitor. Therefore, it is a current sensitive circuit. Spark current is the current that flows directly through the gate and the drain of a MOSFET during a transition of gate voltage. Since it depends on the gate voltage change ratio, dV/dt, not controlled by the gate voltage, the spark current would degrade the performance of circuits such as the charge pump of a phase lock loop when MOSFETs are used as the current control devices in the charge pump. The paper studies the spark current generation mechanism, the asymmetry of the rising edge and the falling edge and the deduction methods.