A digital PWM voltage mode controller integrated circuit (IC) for high-frequency dc-dc switching converters achieving virtually minimum possible, i.e. optimum, output voltage deviation to load transients is introduced. The IC is implemented with simple hardware, requiring small silicon area, and can operate as a single-phase or a two-phase controller. To minimize the area and eliminate known mode transition problems of the optimal response controllers, two novel blocks are combined. Namely, an asynchronous track-and-hold analogto-digital converter (ADC) and a "large-small" signal compensator are implemented. The ADC utilizes a pre-amplifier and only four comparators having approximately eight times smaller silicon area and power consumption than an equivalent windowed flash architecture. The "large-small" signal compensator consists of two parts, a digital PID minimizing small variations and a zero-current detection-based compensator suppressing large load transients. The large-signal compensator requires no extra calculations and has a low sensitivity to parameter variations. It utilizes a synchronization algorithm and the PID calculation results to obtain a bumpless mode transition and stable response to successive load transients. The IC occupying only 0.26 mm 2 silicon area is implemented in a CMOS 0.18µm process and its minimum deviation response is verified with a single and dual-phase 12 V-to-1.8 V, 500 kHz 60/120 W buck converter.I.

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A passive and hardware efficient output capacitor time-constant estimator for digitally controlled dc-dc converters is introduced. The estimator emulates the equivalent RC circuit of the output capacitor with a much smaller version, placed in parallel, and adjusts its own resistance until the two circuits have the same time-constant. The adjustment is based on a very simple zero voltage crossing detection and synchronization with the digital pulse-width modulator operation.The effectiveness of the proposed estimator is illustrated using a 5V-to-1V/5A, 500kHz buck converter demonstrating accuracy within a few tens of ns in the detection of capacitor zero current crossing points.