A 500-MSample/s, 6-bit Nyquist-rate ADC for disk-drive read-channel applications

Abstract

The analog-to-digital conversion required in most disk-drive read-channel applications is designed for good dynamic and noise performance over a wide-input frequency range. This paper presents a 500-MSample/s, 6-bit analog to-digital converter (ADC) and its embedded implementation inside a disk-drive read channel, using a 0.35-/spl mu/m CMOS double-poly (only one poly layer was used in the ADC), triple-metal process. The converter achieves better than 5 effective number of bits (ENOB) for input frequencies up to Nyquist frequency (f/sub in/=f/sub s//2) and sampling frequencies f/sub s/ up to 400 MHz. It also achieves better that 5.6 ENOB for input frequencies up to f/sub s//4 over process, temperature, and power-supply variations. At maximum speed (f/sub s/=500 MHz), the converter still achieves better than 5 ENOB for input frequencies up to f/sub in/=200 MHz. Low-frequency performance is characterized by DNL<0.32 LSB and INL<0.2 LSB. The converter consumes 225 mW from a 3.3-V supply when running at 300 MHz and occupies 0.8 mm/sup 2/ of chip area.