In this paper, we propose a two-step TDC with phase-interpolator and time amplifier to satisfy high resolution at 2.4 GHz input frequency by implementing delay time less than that of an inverter delay. The accuracy of phase-interpolator is improved for process variation using the resistor automatic-tuning circuit. The gain of time amplifier is improved using the delay time difference between two delay cells. It is implemented in a 0.13 µm CMOS process with a die area of 0.68 mm2. And the power consumption is 14.4 mW at a 1.2 V supply voltage. The resolution and input frequency of the TDC are 0.357 ps and 2.4 GHz, respectively.

In this paper, a wide input range CMOS multi-mode active rectifier is presented for a magnetic resonant wireless battery charging system. The configuration is automatically changed with respect to the magnitude of the input AC voltage. The output voltage of the multi-mode rectifier is sensed by a comparator. Furthermore, the mode of the multi-mode rectifier is automatically selected by switches among the original rectifier mode, 1-stage voltage multiplier mode, and 2-stage voltage multiplier mode. In the original rectifier, the range of the rectified output DC voltage is from 9 V to 19 V for an input AC voltage from 10 V to 20 V. In the multi-mode rectifier, the input-range is wider compared to the original rectifier by 5 V. As a result, the rectified output DC voltage ranges from 7.5 V to 19 V for an input AC voltage from 5 V to 20 V. The proposed multi-mode rectifier is fabricated in a 0.35 µm CMOS process with an active area of around 2500 µm 1750 µm. When the magnitude of the input AC voltage is 10 V, the power conversion efficiency is about 94%.