A 10- and 12-Bit Multi-Channel Hybrid Type Successive Approximation Register Analog-to-Digital Converter for Wireless Power Transfer System

This paper presents a successive approximation register (SAR) analog-to-digital converter (ADC) designed for a wireless power transfer system. This is a four–channel SAR ADC structure with 10-bit resolution for each channel, which can also be applied as a single 12-bit ADC. To reduce the area and the number of the required devices in the ADC module, a hybrid-type structure with capacitor and resistor DACs is applied, in which the resistor DAC is shared between channels and determines the seven least significant bits (LSB)s, while the capacitor DAC determines the three most significant bits (MSBs). For the 12-bit operation mode, and to reduce the number of capacitors required in the capacitor DAC, the capacitors of the four channels are shared to determine the five MSBs. A foreground calibration is applied to the capacitor DAC to remedy the gain and offset errors after fabrication. An additional low resistive path is also implemented in the resistor DAC for error correction. The conversion speed for 10- and 12-bit operations reaches up to 1 and 0.5 MS/s, respectively. The prototype ADC is designed in a 180 nm complementary metal-oxide semiconductor (CMOS) process. For 10- and 12-bit operating modes, this ADC module achieves up to 9.71 and 11.76 effective number of bits (ENOBs), respectively.