In this paper, a mode-selectable synchronous buck DC-DC converter with high-efficiency and low-quiescent current is proposed, which is suitable especially for using as a Li-on battery charger. The high efficiency is obtained by applying dynamic power management technology under light-load, which makes some modules of the chip enter to sleep state and the quiescent current of the whole chip down to 45 µA. At the same time, power MOS (Metal-Oxide Semiconductor) devices are also shut down to decrease the dissipation of the system. A simple loop compensation method is also proposed, which can eliminate the influence brought by high equivalent resistance of output's capacitor on the stability of the system loop. The converter has been made with a 0.5 μm CMOS (Complementary Metal-Oxide-Semiconductor) process. Experimental results show that the peak efficiency is 94% at output current 100 mA when the supply voltage is 2.7 V. Moreover, the output voltage can recover within 14 μs at 400 mA load step.

A current reference with complex compensation using negative temperature coefficient of multiple currents is proposed. The principle of compensation is introduced in detail. This work generates two different compensated currents in the whole temperature range, which is different from the traditional curvature-compensated circuit. The compensation is achieved by using difference of the negative temperature coefficients. Piecewise curvature-compensation and higher order nonlinear temperature compensation are applied at the same time. The proposed circuit is simple and easy to implement. Results of simulation with HSPICE show that the achieved temperature coefficient is only 34.2 ppm/°C compared with 364 ppm/°C under 1 μm BCD process, which is unnecessary to compensate in the range of -25°C ∼ 125°C at 5 V supply voltage.