Current parking regulator for zero droop/overshoot load transient response

Supply voltage integrity during a load transition is a critical problem. Droop on the supply may lead to logic failures, and overshoot can reduce reliability. Voltage deviations from the nominal forces designers to apply margins in design to ensure correct operation. This paper addresses two main causes of droop/overshoot on the supply line namely the sluggish converter response and the parasitics between the converter and the load. We present current parking regulator (CPR), a voltage down-converter with almost zero droop or overshoot during a load transient along with implementation techniques to nullify the effect of the parasitics. The underlying principle involves avoiding the inductor slewing time by parking sufficient excess current in the inductor, which is available to use immediately when the need arises. The system design involves on-die, package, and PCB co-design to minimize the impact of parasitics. Measurement results show negligible droop/overshoot when the load current transitions from 0.8A to 7.5A and vice versa in 2ns with only 200nF of load capacitance on the regulated output voltage node. The design was fabricated in a 28nm CMOS technology and integrated in the same package as the load using an 8 layer substrate. It achieves a peak efficiency of 83% at 8A load current.