Categorization and Characterization of Time Domain CMOS Temperature Sensors

Abstract

Time domain complementary metal-oxide-semiconductor (CMOS) temperature sensors estimate the temperature of a sensory device by measuring the frequency, period and/or delay time instead of the voltage and/or current signals that have been traditionally measured for a long time. In this paper, the time domain CMOS temperature sensors are categorized into twelve types by using the temperature estimation function which is newly defined as the ratio of two measured time domain signals. The categorized time domain CMOS temperature sensors, which have been published in literature, show different characteristics respectively in terms of temperature conversion rate, die area, process variation compensation, temperature error, power supply voltage sensitivity and so on. Based on their characteristics, we can choose the most appropriate one from twelve types to satisfy a given specification.

The Design Considerations and Challenges in MOS-Based Temperature Sensors: A Review

“…In this paper, the state-of-the-art MOS-based temperature sensors are categorized according to their thermal sensing principle into three categories, from type I to type III, where the MOSFETs (metal-oxide-semiconductor field-effect transistors) are working in their saturation/linear, subthreshold and gate leakage regions, respectively. This method of categorization is in contrast to [107], which categorizes the delay line-based temperature sensors by their ways of quantization.…”

High-Precision Low-Temperature Drift LDO Regulator Tailored for Time-Domain Temperature Sensors

“…It follows that both architectures for time-domain temperature sensors are sensitive to variations of the supply voltage. Not surprisingly, implementations of such sensors published recently reported supply sensitivities of up to 1600 • C/V, leading to temperature errors of up to +/−4 • C [3].…”

“…Most time-domain temperature sensors employ conversion rates between 1 kHz and 10 kHz [3], to avoid self-heating effects which may degrade the sensor performance [33]. Therefore, the PSR performance of the LDO should be optimized for these frequencies: at least 80 dB up to 1 kHz and 40 dB at 10 kHz.…”

“…However, for fine CMOS processes operating at low supply voltages, time-domain sensors yield better performance. A recent survey [3] of this trend analyses no less than 23 such sensors reported recently, identifying 12 topologies.…”

“…Time-domain sensors operate by comparing a temperature-dependent time-related parameter of a signal with a temperature-independent one. Therefore, these sensors can be classified into two broad categories considering the signal parameter they exploit: delay time and clock period [3]. Figure 1 presents the block diagrams for these sensor categories.…”