Constant on-time DC-DC converter using ripple injection filter with inherent adaptive voltage positioning

A constant on-time DC-DC converter using ripple injection filter with inherent adaptive voltage positing function is proposed. By using the proposed filter, voltage positioning is realized without current-sensing mechanism and the droop voltage can be controlled by a resistor within the filter. The droop voltage is calculated and the filter design methodology to obtain optimal transient response is described. A test chip for 1-A, 3.6-V to 1.2-V DC-DC converter is fabricated using 0.25-μm CMOS process. The experimental results show that the line regulation of the designed DC-DC converter is 37mV/A which matches the calculation. With a load-current transient of 500mA, the designed DC-DC converter showed voltage disturbance of 15mV.