A 10-MHz Current-Mode AOT Boost Converter With Dual-Ramp Modulation Scheme and Translinear Loop-Based Current Sensor for WiFi IoT Applications

In this article, a dual-ramp modulation scheme is proposed to solve an instability during the discontinuous conduction mode (DCM) operation of current-mode constant on-time (COT) controlled boost converters. A duty cycle-dependent auxiliary waveform, which is generated by the proposed capacitor-coupled common-drain amplifier (CCCDA), is summed with an inductor current information to form a current feedback loop. With the proposed scheme, the pulse frequency modulation (PFM) operation can be spontaneously accompanied by the current-mode COT control to enhance a light-load efficiency. In addition, a translinear loop (TLL)-based valley current sensor is introduced to sense a valley inductor current while solving the response time and stability problems of the previous SenseFET-based current sensor. An adaptive ON-time (AOT) generator provides a quasi-fixed switching frequency in the CCM operation regardless of the conversion ratio. The proposed boost converter has been fabricated using a 0.18-mu m CMOS process with a total chip area of 1.23 mm x 1.37 mm. It achieves a peak efficiency of 94.5% even at a high-switching frequency of 10 MHz, and smooth mode transition between PFM and pulsewidth modulation (PWM) operations depending on the load conditions.