This paper presents a sub-1 V CMOS bandgap voltage reference that accounts for the presence of direct tunneling-induced gate current. The total chip size is 0.063 with a standard 0.13- CMOS process. The measured power-supply rejection ratio (PSRR) of 30 dB is achieved at the frequency of 100 kHz. The average TC for 8 random samples is approximately 9.3. This curvature correction circuit causes the proposed BGR circuit without any trimming to show a measured temperature coefficient (TC) as low as 4.2 over a wide temperature range of 160 at a power supply voltage of 1.2 V. The summation of these reference voltages is proposed to achieve a high-order curvature compensation. Selection of the appropriate resistances in the BGR cores results in one reference voltage with a well balanced curvature-down characteristic and another reference voltage with an evenly balanced curvature-up characteristic. A current-mirror circuit is proposed to implement one of the BGR cores to have the curvature-up characteristic. Two BGR cores adopt conventional structures with the curvature-down characteristics. The proposed BGR circuit consists of two BGR cores and a curvature correction circuit, which includes a current mirror and a summing circuit. This study presents a high-precision CMOS bandgap reference (BGR) circuit with low supply voltage.
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Measurements show that the sensor interface achieves a thermal variation of 178ppm/☌ over ☖0mV input full scale and a thermal variation of 65ppm/☌ over ±40mV input full scale over a wide operation temperature range extended from -20☌ to 220☌. The sensor interface is fabricated using a 0.18µm Partially-Depleted Silicon on Insulator technology (PD-SOI) from XFAB which is chosen for its thermal robustness. The sensor interface output depends only on the ratio of its parameters values rather than their absolute values thus leading to a low temperature dependency. A pair of ILOs converts the sensor output voltage into a phase shift difference which is then digitized using a time to digital converter. The sensor interface is based on Injections Locked Oscillators (ILO) used as phase shifters. This approach offers the advantage of better thermal stability compared to typical analog based architectures.
The sensor interface has a fully differential time domain architecture. A high temperature integrated sensor interface is proposed.
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