A 0.90–4.39-V Detection Voltage Range, 56-Level Programmable Voltage Detector Using Fine Voltage-Step Subtraction for Battery Management

A 6.4 nW 1.7% Relative Inaccuracy CMOS Temperature Sensor Utilizing Sub-Thermal Drain Voltage Stabilization and Frequency-Locked Loop

“…For applications that cannot provide the reference voltage, a CMOS voltage reference [8] is implemented on the same chip. The measured power consumption of the voltage reference is 2.2 nW.…”

A Subthreshold Voltage Reference with Coarse- Fine Voltage Trimming

“…To meet these requirements, there has been significant recent interest in ultra-low power references. Among these references are subthreshold references [1][2][3][4][5][6][7][8][9][10], such as the 2T transistor-based voltage reference shown in Figure 1 [1,2,3,7,10].…”

“…Another version of this circuit uses the native zero threshold device which can produce a reference voltage independent of Vdd with only two transistors [10]. Several other versions of these references have been published using different Vth in the process [9]. Although the 2T references are very attractive due to their simplicity and ultra-low power (pW range), they have not yet found acceptance in most systems.…”

“…There have been several papers which have demonstrated trimming of the temperature coefficient [1,2,3,4,6,7,10]. However, only a few have shown precision trimming of the reference voltage itself [1,8,9]. Lin has demonstrated that multiple voltage references can be generated from the same circuit [1].…”

“…Someya has shown voltage trimming using stacked Vgs transistors to achieve a voltage resolution of 50mV [8]. In a follow-up paper [9], Someya utilized resistors to achieve a resolution of 5mV, but these resistors required a very large area to obtain high enough resistance for nW level power.…”