A High Efficiency Re-configurable Step-down Switched Capacitor DC-DC Converter for Medical Implants Application

Abstract

In this paper, a re-configurable switched-capacitor DC-DC converter which features high efficiency, small silicon area and low voltage ripple is designed. The switched-capacitor based converter has inherently superior counter electromagnetic interference (EMI) capability, which is important for medical implants. This converter utilizes a self-adaptation mechanism to switch between normal pulse frequency modulation (PFM) and SKIP modes. This mechanism optimizes the power consumption by shielding part of the clock to based on load current conditions. Simulation results show that the output voltage settles around 2.4V with +1.6/-5% error when the input voltages are 2.5V, 3.7V, and 4.9V, respectively. Peak efficiency of 97% and average efficiency of 93% have been achieved in normal mode 2-15mA load current. For light load, i.e.<2mA load, the efficiency of SKIP mode has been improved. The SC converter IC is then implemented in a 180 nm 5V standard CMOS process.