A 1-GHz, multibit, continuous-time, delta–sigma ADC for Gigabit Ethernet

In this work the design of a continuous-time ΔΣΔΣ modulator for Gigabit Ethernet applications is presented. The input bandwidth and oversampling ratio are, respectively, 62.5 MHz and 8, resulting in a clock frequency of 1 GHz. It was designed and implemented in a standard 90 nm CMOS technology. The active area of the modulator measures 0.0207mm2. It consists of a loop filter based on RC-opamp integrators and a 3-bit quantizer which includes a data weighted averaging scrambler. A digital tuning scheme to deal with process variations has also been included. System level simulations including several non-ideal effects have been carried out in order to determine in detail the performance of the converter. Experimental results show a resolution of 7.1 effective bits, and a power consumption of 10.8 mW from a nominal power supply of 1 V.