Abstract
In this paper, we propose a hybrid CMOS and phase-change memory (PCM)-relaxation-oscillator based circuit for temperature-sensing applications. Unlike conventional CMOS temperature sensors based on ring- or relaxation-oscillators, the proposed sensor does not require any curvature calibration technique for linearity improvement of the thermal response. The presented system explores the temperature dependence of Ovonic-threshold-switching voltage (Vth) and DC OFF state resistance (ROFF) of a PCM device. The proposed temperature sensor exhibits a resolution of ∼0.04 °C (for the 0 °C to 80 °C temperature range) with 0.51 nJ energy consumption per conversion in simulations.
Highlights
Temperature sensing is a critical feature for various on-chip applications such as Internet-of-things (IoT), ubiquitous healthcare (U-healthcare),1–3 radio frequency identification (RFID) tags,4–6 environmental and structural monitoring,7,8 and 3D integrated circuits (ICs).9,10 High accuracy, fast thermal response time, linear output response, high resolution, and sensitivity are key requirements of an ideal temperature sensor
We propose a hybrid CMOS and phase-change memory (PCM)-relaxation-oscillator based circuit for temperature-sensing applications
The oscillatory behavior can be explained as follows: (i) Initially, when a constant DC supply is applied, the node voltage V0 starts increasing because of the capacitor (Cl) charging through the resistor Rs. (ii) Once the voltage (V0) across the capacitor reaches the Vth level, the PCM device operates in an unstable OTS induced NDR region and the capacitor Cl starts discharging toward Vh. (iii) As soon as V0 reaches the hold voltage, the PCM device returns to the OFF state; Cl again starts charging and maintains the complete cycling behavior of charging and discharging [Fig. 1(c)]
Summary
Temperature sensing is a critical feature for various on-chip applications such as Internet-of-things (IoT), ubiquitous healthcare (U-healthcare), radio frequency identification (RFID) tags, environmental and structural monitoring, and 3D integrated circuits (ICs). High accuracy, fast thermal response time, linear output response, high resolution, and sensitivity are key requirements of an ideal temperature sensor. CMOS compatible bipolar transistors (BJTs) were used for thermal sensing based on temperature-to-voltage conversion.. CMOS compatible bipolar transistors (BJTs) were used for thermal sensing based on temperature-to-voltage conversion.11 These sensors, owing to their poor conversion accuracy, required additional on-chip analog-todigital converters (ADCs) for calibration, increasing their complexity and die-footprint.. Some time-domain temperature sensing techniques such as pulse proportional to absolute temperature (PTAT) and voltage-controlled-oscillator (VCO) based time-to-digital converters (TDCs) have been explored. Various metal and semiconductor based thermal sensors are commercially available in the market.. Various metal and semiconductor based thermal sensors are commercially available in the market.19,20 These sensors work based on the thermoresistive effect, i.e., change in electrical resistance with temperature. We propose a hybrid CMOS and PCM-relaxation-oscillator (RxO) based thermal sensor for embedded temperature-sensing applications These sensors provide a high temperature coefficient of resistance (TCR), the fabrication cost and complexity might be higher in some cases. Recently, hybrid CMOS-NVM (non-volatile memory) based thermal sensors have been explored. In this study, we propose a hybrid CMOS and PCM-relaxation-oscillator (RxO) based thermal sensor for embedded temperature-sensing applications
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