A CMOS multi-bit sigma-delta modulator for video applications

This paper describes the design of a sigma-delta modulator with 5-bit quantizer for analog to digital conversion in video applications. A single poly, 0.35 µm CMOS process is used. Most of the quantization noise of a sigma-delta modulator is shifted to higher frequencies by noise shaping. The resulting output spectrum corresponds well with the noise sensitivity of the human eye which is less sensitive to high frequency noise. The realized sigma-delta modulator has an excellent low frequency performance, the DNL is 0.51 LSB@10 bit level and the integrated noise up to 1 MHz is 60 dB below the maximum signal power. The SNR (noise integrated over total band of 6.75 MHz) is 43.6 dB.