A High-Precision CMOS Temperature Sensor

Ultra-low-power (ULP) sensor technologies for the future internet of things have presented challenges in ULP implementation of reference circuits while keeping traditional requirements of stable performance. For voltage reference circuits, as an essential block in SoCs to generate various internal supply voltages, the bandgap voltage-reference (BGVR) scheme has been widely used since it provides a well-defined value with strong immunity to process/voltage/temperature variations. Nanowatt-consuming BGVR circuits have been recently proposed using a capacitor network [4] and a leakage-based proportional-to-absolute-temperature (PTAT) circuit [5]. On the other hand, the current reference circuit that is required to set internal bias current still presents difficulties in achieving both stable performance and ULP consumption. The general approach to building a current reference is to use a BGVR with additional resistors for V-to-I conversion. Though it can provide a well-defined stable current reference, it also requires excessively large resistance for ULP consumption. Another approach is a CMOS-based current reference circuit that tries to make the exponential term in the subthreshold current equation constant or temperature-independent, hence reducing process and temperature dependencies. While CMOS reference circuits have achieved ULP implementations, the current is still determined by a number of process and design parameters, resulting in large sensitivity to process variations. This paper presents a sub-10nW bandgap-reference (BGR) circuit that implements both voltage and current references in one circuit. The BGR circuit is implemented with a 0.18µm CMOS process and generates voltage and a current references of 1.238V and 6.64nA while consuming 9.3nW. The voltage and current references show standard deviations of 0.43% and 1.19% with temperature coefficients of 26ppm/°C and 283ppm/°C, respectively.

A high-precision current-mode bandgap reference (BGR) circuit with a high-order temperature compensation is presented in this paper. In order to achieve a high-precision BGR circuit, the equation of the nonlinear current has been modified and the high-order term of the current flowing into the nonlinear compensation bipolar junction transistor (NLCBJT) is compensated further. According to the modified equation, two solutions are designed to improve the output accuracy of BGR circuits. The first solution is to divide the NLCBJT branch into two branches to reduce the coefficient of the nonlinear temperature compensation current. The second solution is to inject the nonlinear current into the two branches based on the first one to further eliminate the temperature coefficient (TC) of the current flowing into the NLCBJT. The proposed BGR circuit has been designed using the Semiconductor Manufacturing International Corporation (SMIC) 55 nm CMOS process. The simulation results show that the variations in currents flowing into NLCBJTs improved from 148.41 nA to 69.35 nA and 7.4 nA, respectively, the TC of the output reference current of the proposed circuit is approximately 3.78 ppm/°C at a temperature range of -50 °C to 120 °C with a supply voltage of 3.3 V, the quiescent current consumption of the entire BGR circuit is 42.13 μA, and the size of the BGR layout is 0.044 mm2, leading to the development of a high-precision BGR circuit.

This paper proposes a novel curvature‐correction technique insensitive to process variations, which can be used in not only the bandgap reference (BGR) circuit but also the Zener reference circuit. By using two BJT transistors to form a differential pair structure, the current difference between the differential pair generates a compensation current, which compensates for the non‐linearity in the reference voltage. Unlike the classic curvature‐correction technique which can only be used in the BGR circuit, this novel technique can be used in the Zener reference circuit as well. What is more, the proposed curvature‐correction technique is insensitive to process variations, which greatly increases the reliability of commercial products. Finally, simulation results verify the validity of the proposed technique.

A high precision band-gap reference (BGR) with piecewise-linear compensation is designed in this paper. A low voltage Brokaw BGR architecture is employed to provide low output voltage. A high gain, low power supply rejection ratio (PSRR) operational amplifier is designed to improve the PSRR of the band-gap reference. In order to achieve temperature stability significantly lower than the traditional band-gap reference, a circuit which produces a current with positive temperature coefficient (TC) at high temperatures and 0 current at lower temperatures is designed. The whole BGR circuits are simulated by Spectre based on chartered 0.18μm 1P5M 1.8V CMOS technology. It's clear from simulation result that the TC of the output reference voltage approaches 2.61ppm/K over the military temperature range, the PSRR reaches 107.2dB at low frequency (f=0.1HZ), the whole BGR dissipates 0.4mW. In addition, the output reference voltage changes only 8.6μV when the power supply changes from 1.5V to 2.1V, that is to say, the power regulation ratio is 0.014mV/V.

The accelerated aging stress test is essential for assessing the reliability and quality of band gap reference (BGR) circuits, which are crucial for maintaining consistent voltage references in ICs. In this study, we present accelerated aging analysis of a classic BGR design as an case study. A BGR circuit, validated on a Quality and Reliability On-Chip (QROC) platform, demonstrated temperature coefficient of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.12 \text{ mV} /{}^{\circ} \mathrm{C}$</tex> across 25° C to 100° C, ensuring minimal drift with temperature fluctuations. The output reference voltage <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(V_{{ref}}) 646$</tex> mV was measured over a supply voltage range of 0.8V to 1.4V, with a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pm 7.5 \text{ppm} / \mathrm{V}$</tex>. The circuit's robustness was further confirmed by observing only a 1% change in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{{ref}}$</tex> after a million-second stress test at varying temperatures and a stress voltage 1.4V. This result, showing less than 6.5% deviation from post-layout simulations, underscores the BGR's resilience and precision, highlighting the importance of such stress testing in predicting IC performance and longevity.

A BiCMOS current source reference network which eliminates the impact of DC power supply voltage drops on the operation of ECL (emitter coupled logic) circuits is described. This is essential for implementing ECL design techniques in ULSI BiCMOS circuits. Using the current source network, reference voltages are generated locally, so that the ECL voltage references are correctly referenced to the local power supply potentials. A power-supply-insensitive bandgap reference generator is used to generate precision on-chip voltage references and current sources. The bandgap reference circuit uses both MOS and bipolar transistors and is much simpler than a similar design using bipolar-only circuitry. The micrograph of the test chip containing the bandgap circuit nd BiCMOS op amp analog drivers is shown. The drivers are designed for multiple-reference-level regeneration. The test chip has been fabricated using a 0.8- mu m BiCMOS process. The typical characteristics of the bandgap circuit and the analog driver are shown. >

The reference voltage is a core part of RFID tags, its performance directly determines the whole chip's life and performance. The temperature coefficient is one of the important performances of the reference voltage source and the high-order temperature compensation is an effective method to reduce the temperature coefficient of the reference source. A low temperature coefficient bandgap reference is designed based on the standard 65nm CMOS process, and the low-supply voltage operation with bandgap reference circuit with current mode structure. The designed CMOS bandgap voltage reference is in the range of -20°C to 100°C with temperature coefficient of 9.6 ppm/°C and provides a good Power Supply Rejection Ratio(PSRR) of 79dB in the low frequency. The results of simulation show that the design improve the performance of the bandgap reference voltage source effectively.

A novel band-gap reference circuit is presented in order to reduce the offset voltage and power consumption. By using the op-amp input voltage as part of the reference voltage source, the gain and power supply rejection ratio of the op-amp is increased. The working principle of the Band-gap reference circuit is analyzed, and it is pointed out that the temperature coefficient becomes smaller through using the temperature compensation. The simulation results based on xiyue 0.3um bipolar process show that the circuit has low power dissipation and good temperature characteristic, the power supply rejection ratio is up to 92dB. The correctness of the theoretical analysis is verified by simulation results.

This paper presents a curvature-compensated bandgap reference (BGR) circuit implemented in 0.35 /spl mu/m CMOS technology. The circuit delivers an output voltage of 1.09 V and achieves a temperature coefficient of 3.1 ppm//spl deg/C over [-20/spl deg/C, 100/spl deg/C] after trimming, a power supply rejection ratio of -80 dB at 1 KHz and an output noise level of 1.43 /spl mu/V/sqrt(Hz) at 1 KHz. The BGR circuit consumes a current of 37 /spl mu/A and the power supply ranges from 1.5 V to 3.3 V.

This article presents a low-power bandgap reference (BGR) featuring high power supply rejection ratio (PSRR) and fast start-up capability, operating across a wide supply voltage range of 1.3–5 V. A novel prebiased pulse current injection technique is proposed in the start-up circuit, achieving a 1% settling time of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\mu $</tex-math> </inline-formula>s and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$25\times $</tex-math> </inline-formula> speed gain during start-up. To enhance supply noise immunity, the proposed BGR employs a preregulated (PR)-based amplifier that effectively decouples the reference voltage from supply voltage fluctuations. Fabricated in a 0.18-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula>m BCD process, the proposed reference occupies an active area of 0.0394 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. Under a 5 V supply, the circuit generates a 1.2 V reference voltage while consuming only 48 nA quiescent current. Operating down to a minimum supply voltage of 1.3 V, it maintains a low power consumption of 57.2 nW at room temperature. The reference exhibits an average temperature coefficient (TC) of 5.95 ppm/°C across a wide temperature range (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$- 40~^{\circ }$</tex-math> </inline-formula>C to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$125~^{\circ }$</tex-math> </inline-formula>C) and achieves an outstanding line sensitivity (LS) of 0.00308%/V over the 1.3–5 V supply range. Furthermore, the measured PSRR reaches −85 dB at 100 Hz.

Based on 180 nm commercial BCD process, the effects of single event transient effect on bandgap reference circuit are studied and simulated, and a radiation-hardened-by-design based on dual modular redundancy technology is proposed to mitigate the effects of SET. The SET detection circuit composed of built-in threshold comparator is used to realize real-time dynamic detection of reference voltage, and the influence of SET is further isolated by pulse widening technology, which ensures that the reference voltage can recover quickly under small jump when BGR is incident by high-energy particle. The experimental results show that under the input voltage range of 2.9 V∼4.5 V and the linear energy transfer value of high-energy particles is equal to 100 MeV·cm2/mg, the maximum jump of reference voltage caused by SET decreases from 2.791 V to 38 mV, the recovery time decreases from 800 ns to 18 ns, and the SET mitigation ability reaches 98.3%. Compared with the traditional RC hardening scheme, this method has obvious advantages, the area optimization is 28.09%, and the recovery time is increased by more than 99%.

With Inner Tracking System v3 (ITS3), the ALICE experiment is pursuing a wafer-scale Monolithic Active Pixel Sensor (MAPS). The chip is being developed in TPSCo 65 nm ISC technology which is under study in the framework of CERN EP R&D on monolithic sensors for High Energy Physics (HEP) applications. This contribution presents designs and measurement results of building blocks needed for this chip, in particular bandgap references and temperature sensors. In addition, simulation results of the design of Low Drop-out Regulator (LDO) to be submitted for the next prototyping run will be discussed.

A high-order curvature-compensated CMOS bandgap reference (BGR) topology with a low temperature coefficient (TC) over a wide temperature range and a high power supply reject ratio (PSRR) is presented. High-order correction is realized by incorporating a nonlinear current INL, which is generated by ∆VGS across resistor into current generated by a conventional first-order current-mode BGR circuit. In order to achieve a high PSRR over a broad frequency range, a voltage pre-regulating technique is applied. The circuit was implemented in CSMC 0.5 μm 600 V BCD process. The experimental results indicate that the proposed topology achieves TC of 0.19 ppm/°C over the temperature range of 165 °C (−40 to 125 °C), PSRR of −123 dB @ DC and −56 dB @ 100 kHz. In addition, it achieves a line regulation performance of 0.017%/V in the supply range of 2.8–20 V.

Bandgap reference (BGR) circuits are widely used due to their stable output voltage over process, supply voltage and temperature variations. Reference voltage stability is critical for data-acquisition applications and lower supply voltages can reduce the power of mixed-signal systems. However BGR for analog circuits is one of the bottlenecks for sub-1V supply operation because BGR supply voltage is limited by V EB +V DS [1]. V EB refers to the emitter-base voltage of a pnp transistor which is limited to ~0.6 to 0.7V due to silicon junction cut-in voltage, while V DS is the drain-source saturation voltage of a current-mirror. The BGR temperature dependence is decided by the weighted sum of proportional-to-absolute-temperature(PTAT) and complementary-to-absolute-temperature (CTAT) terms. An alternative PTAT generator can be implemented by dV GS (gate-to-source voltage difference) of a MOS pair in subthreshold [2]. The CTAT generator can be implemented by special devices or using the gate-source voltage V GS of subthreshold MOSFETs. Although the V GS of a subthreshold MOSFET is smaller than emitter-base voltage of a pnp transistor, the MOSFET model inaccuracy in the subthreshold region and high process-dependent characteristic of MOSFET gate-source voltage induces high variation for voltage reference circuits.

An Offset Canceled Bandgap Reference (BGREF) circuit is reported in TSMCs 28nm technology node. This BGREF has a 3-sigma untrimmed inaccuracy of ±0.534% with a power consumption of 58uW and an estimated area of 2142um2 which is one of the smallest BGREFs reported. The BGREF uses a closed loop circuit with a Folded Cascode Amplifier.