Design of a 12-bit high-speed CMOS D/A converter using a new 3D digital decoder structure useful for wireless transmitter applications

Abstract

In this paper a 12-bit Nyquist current-steering digital-to-analog converter (DAC) is implemented using TSMC 0.35 lm standard CMOS process technology. The proposed DAC is an essential part in baseband section of wireless transmitter circuits. Using oversampling ratio (OSR) for it leads to avoid use of an active analog reconstruction filter. The optimum segmentation (75%) has been used to get the best DNL and reduce glitch energy. This segmentation ratio guarantees the monotonicity. Higher performance is achieved using a new 3D thermometer decoding method which reduces the area, power consumption and the number of control signals of the digital section. Using two digital channels in parallel, helps reach 1 GHz sampling frequency. Simulations indicate that the DAC has an accuracy better than 10.7-bit for upcoming higher data rate standards (IEEE 802.16 and 802.11n), and a spuriousfree-dynamic-range (SFDR) higher than 64 dB in whole Nyquist frequency band. The post layout four corner MonteCarlo simulated INL is better than 0.74 LSB while simulated DNL is better than 0.49 LSB. The analog voltage supply is 3.3 V while the digital part of the chip operates with only 2.4 V. Total power consumption in Nyquist rate measurement is 144.9 mW. Active area of chip is 1.37 mm 2 .