A 10-b 100-kS/s 1-mW General-Purpose ADC for Cellular Telephones

An on-demand general-purpose analog-to-digital converter (GPADC), which achieves a 10-b accuracy of up to 100-kS/s request rate, is presented. The GPADC can process single-ended signals with selectable input ranges up to the battery voltage. The range selection accuracy is 1 LSB. The DAC architecture presents the benefits of a differential approach while sampling single-ended input signals. Built-in reference buffer and oscillator are included. An external clock source is not needed; only a conversion request signal is necessary. Dedicated low-power design solutions have been introduced to reduce power consumption at the maximum conversion request speed to about 1 mW at a 2.0-V supply voltage. New design solutions have been introduced to comply with system-level requirements, such as scaling and shifting of the battery voltage, buffering low-frequency input signals with high source impedance, and to cope with the presence of input signals with voltage levels higher than the GPADC supply voltage when the battery is discharged. The active area is about 0.58 mm2 in a 0.35-μm single-poly 5-metal CMOS technology with a MIM capacitor option.