Switched-capacitor converter with low dropout voltage regulator for wireless sensor nodes

A 1V unregulated DC voltage from the rectifier of an energy harvesting node is converted down to 650mV regulated DC voltage with 10mV ripple (maximum frequency is 100MHz) by the switched-capacitor converter (SCC) that can supply up to 2.5mA current. For more supply sensitive loads such as RF blocks, a low dropout (LDO) voltage regulator steps down the SCC's output to 500mV regulated DC voltage with at most 1.4% ripple. The LDO can supply a maximum load current of 1mA with 0.98% load regulation. Simulation results in 90nm CMOS show that the SCC has a maximum efficiency of 71% while the LDO has a maximum efficiency of 70.8% at maximum load current.