A Multi-Phase Switched-Capacitor Converter for Fully Integrated AMLED Micro Display System

摘要： A fully-integrated switched-capacitor (SC) DC-DC converter is designed for powering up an active-matrix light-emitting diode (AMLED) micro-display system. Stacking-transistor technique with three voltage conversion ratios is utilized to handle the lithium-ion battery range of 2.6 V to 4.2 V and to reduce the switching loss. A 101-phase interleaving scheme is adopted such that (1) output voltage ripple ΔVO is significantly reduced; (2) no external output capacitor is needed; and (3) SC power-cells are physically cascaded to encircle the LED array and drivers to reduce conduction loss. Two test chips were designed in 0.18 μm 1P6M CMOS technology. The first chip is a test chip consisted of the SC converter only. The output voltage is 4.2V and the measured maximum ΔVO is 52 mV. The measured power density is 74.4 mW/mm2, peak efficiency is 81%, and maximum output power is 258 mW. The second chip is a system chip integrating the SC converter with the AMLED array and drivers using flip-chip packaging. The converter delivers a maximum power of 216 mW with a 78% peak efficiency in the SC mode and a 91% peak efficiency in the linear regulator mode.