Abstract
A voltage reference is strictly required for sensor interfaces that need to perform nonratiometric data acquisition. In this work, a voltage reference capable of working with supply voltages down to 0.5 V is presented. The voltage reference was based on a classic CMOS bandgap core, properly modified to be compatible with low-threshold or zero-threshold MOSFETs. The advantages of the proposed circuit are illustrated with theoretical analysis and supported by numerical simulations. The core was combined with a recently proposed switched capacitor, inverter-like integrator implementing offset cancellation and low-frequency noise reduction techniques. Experimental results performed on a prototype designed and fabricated using a commercial 0.18 μm CMOS process are presented. The prototype produces a reference voltage of 220 mV with a temperature sensitivity of 45 ppm/°C across a 10–50 °C temperature range. The proposed voltage reference can be used to source currents up to 100 μA with a quiescent current consumption of only 630 nA.
Highlights
CMOS Bandgap Voltage Reference forIn the era of the Internet of Things (IoT), the development of nonintrusive wearable biomedical devices is stimulating research in many different fields, including that of integrated electronic circuits [1,2,3,4]
An optical micrograph of the proposed voltage reference is shown in Figure 8, where the layout is superimposed on the picture
It was shown that direct replacement of the Bipolar Junction Transistor (BJT) with low-threshold MOSFETs in the popular Kuijk bandgap core [15] is not a viable solution to obtain Voltage Reference (VR) compatible with ultralow supply voltages
Summary
In the era of the Internet of Things (IoT), the development of nonintrusive wearable biomedical devices is stimulating research in many different fields, including that of integrated electronic circuits [1,2,3,4]. The drawback of this kind of VR is that depletion MOSFETs are not available in most modern CMOS processes Another popular approach is biasing a diode-connected MOSFET with a current that has a properly tailored temperature dependence such that the typical CTAT dependence of the threshold voltage is canceled [31]. The feedback connection required by this class of VRs is provided in the prototype by a recently introduced switched capacitor integrator, having an always-available output voltage and intrinsic offset and flicker noise cancellation [34] This integrator was already used in the combination of a BJT bandgap core in a differential-output VR designed for the 1.4–3.3 V Vdd range [35]. The results of the measurements performed on the prototype are described, demonstrating that a reference voltage with low sensitivity with respect to temperature and supply voltage can be obtained with the proposed approach
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