On-chip Type III compensator by using constant-Gm OTAs and capacitor-multipliers for fully integrated Buck converters

For low cost and high integration, an on-chip compensator implemented in a Buck converter with minimized external pins and high performance is proposed. Trans-conductance amplifiers with constant G_m and high linearity are developed to substitute the resistors; meanwhile capacitance multipliers consisting of high-gain amplifiers are designed to replace the capacitors. Thus, all passive devices in compensator are fully integrated on chip. The Buck converter is designed by using a standard 0.35 μm CMOS process. The stability of the loop is verified by theoretical analysis and measurement results. It not only keeps good transient response of the fundamental Type III compensator, while tremendously reduces the chip area. Measurement results show the good performance of loop stability and fast transient response. The peak efficiency is up to 94.3%.