A 0.3–1.2 V Schottky-Based CMOS ZTC Voltage Reference

A voltage reference based on MOSFETs operated under Zero Temperature Coefficient (ZTC) bias is proposed. The circuit operates in a power supply voltage range from 0.3 V up to 1.2 V and outputs three different reference voltages using Standard-VT (SVT), Low-VT (LVT), and Zero-VT (ZVT) MOS transistors biased near their ZTC point by a single PTAT current reference. Measurements on 15 circuit samples fabricated in a standard 0.13-μm CMOS process show a worst-case normalized standard deviation (σ/μ) of 3% (SVT), 5.1% (LVT) and 10.8% (ZVT) respectively with a 75% of confidence level. At the nominal supply voltage of 0.45 V, the measured effective temperature coefficients (TCeff) range from 140 to 200 ppm/oC over the full commercial temperature range. At room temperature (25 oC), line sensitivity in the ZVT VR is just 1.3%/100 mV, over the whole supply range. The proposed reference draws around 5 μW and occupies 0.014 mm
²
of silicon area.