A 3.3-V, 15-bit, delta-sigma ADC with a signal bandwidth of 1.1 MHz for ADSL applications

Abstract

The design of a high-resolution, high-speed, delta-sigma analog to-digital converter that operates from a single 3.3-V supply is presented. This supply voltage presents several design problems, such as reduced signal swing and nonzero switch resistance in the switched-capacitor circuits. These problems are tackled in this design by a careful optimization at the system level and by a detailed analysis of several circuit nonidealities. The converter uses a 2-1-1 cascade topology with optimized coefficients. For an oversampling-ratio of only 24, the converter achieves a signal-to-noise ratio of 87 dB, a signal-to-(noise+distortion) ratio of 82 dB, and an input dynamic range of 15 bits after comb filtering. The converter is sampled at 52.8 MHz, which results in the required signal bandwidth for asymmetrical digital subscriber line applications of 1.1 MHz. It is implemented in a 0.5-/spl mu/m CMOS technology, in a 5-mm/sup 2/ die area, and consumes 200 mW from a 3.3-V power supply.