A 960MS/s DAC with 80dB SFDR in 20nm CMOS for multi-mode baseband wireless transmitter

A 960MS/s calibrated digital-to-analog converter (DAC) and low pass reconstruction filter are fabricated in 20nm CMOS. The calibration is implemented without an extra analog-to-digital converter (ADC) by reconfiguring the filter as the integrator for an incremental ADC which is used to digitize DAC cell mismatch. The digital input to the DAC is compensated by a look-up table to correct DAC mismatch in real-time. Before calibration, DNL is −1.1/+0.7LSB and INL is −2.1/+0.3LSB. After calibration DNL and INL are improved to −0.2/+0.2LSB and −0.3/+0.2LSB respectively. This 10b DAC achieves 80.2dB SFDR after calibration, and occupies 0.01mm
²
for an I/Q DAC pair which is 12.5% of the area for an uncalibrated I/Q DAC pair.