A mixed-signal pulse width modulator for portable SMPS applications

This paper presents a design for a mixed-signal pulse width modulator (MSPWM) integrated circuit that targets the digital control of high-frequency switched-mode DC-DC power supplies (SMPS). Previous designs consider digital pulse width modulators (DPWM) implementations that encounter important design issues, such as power consumption, non-linearity, layout dependency, trimming capability and temperature dependency. This work presents effective solutions, suitable for large-scale production of ICs, since it combines high-precision, high-linearity and temperature-independent standard analog circuits, which are commonly offered by the semiconductor industry, with the simplicity and reuse of digital PID compensation as input. The 8-bit prototype designed for a 0.18-μm CMOS process operates at switching frequency of 2 MHz, draws only 96.25 μA from a 1.8 V supply and takes 0.029 mm2, including the non-overlapping control logic of SMPS power devices.