Cascode buffer for monolithic voltage conversion operating at high input supply voltages

A high-to-low switching DC-DC converter that operates at input supply voltages up to twice the maximum voltage permitted in a nanometer CMOS technology is proposed. The circuit technique is based on a cascode bridge that maintains the steady-state voltage differences among the terminals of all of the transistors within a range imposed by a specific fabrication technology. The proposed circuit technique permits the full integration of active and passive devices of a switching DC-DC converter with a high voltage conversion ratio in a standard low voltage CMOS process. An efficiency of 87.8% is achieved for 3.6 V to 0.9 V conversion, assuming a 0.18 μm CMOS technology. The DC-DC converter operates at a switching frequency of 97 MHz while supplying a DC current of 250 mA to the load.