Calibration technique tracking temperature for current-steering digital-to-analog converters

In this paper, a novel foreground calibration technique is presented for current-steering DACs. Each current source is in parallel with a CAL DAC injecting a small correction current that corrects the mismatch and tracks the temperature variations. High matching accuracy is not only achieved at the calibration temperature, but also maintained across a wide operating temperature range from -40 °C to 120 °C. A 14-bit DAC is designed in a standard 65nm CMOS process to verify the concept. The transistor level simulation results show that the new calibration technique reduces the worst case INL and DNL of the DAC across the whole temperature range by a factor of 15.7 and 12.8 compared with the intrinsic matching and by a factor of 2.9 and 2.8 compared with the conventional calibration method [1]. The DAC achieves real 14-bit level INL and DNL across a wide temperature range with only 10-bit level raw matching.