A Two-Parameter Calibration Technique Tracking Temperature Variations for Current Source Mismatch

Abstract

This brief presents a foreground calibration technique for current source mismatch that is insensitive to temperature variations. Two calibration digital-to-analog converters (CAL DACs) provide correction currents to compensate two current source mismatch components caused by the threshold voltage mismatch and the current factor mismatch. Each CAL DAC has the same temperature dependence as its corresponding mismatch component. The sum current of the two CAL DACs automatically tracks the temperature variations of the current source mismatch with no need for temperature information. To obtain the CAL DAC input codes, two different bias current settings are used instead of calibrating at two separate temperatures. This scheme significantly reduces the calibration time and cost. A 16-bit DAC with this calibration technique is fabricated in a 65-nm CMOS process. The measurement results show that the matching of the most significant bit currents is improved from intrinsic 12 to 16 bits across the temperature range from −40 °C to 85 °C. The proposed calibration technique achieves superior temperature stability compared to the previously published schemes.