Nano‐ampere PTAT current source with temperature inaccuracy <±1°C

Abstract

The architecture for generating a nano-ampere proportional to absolute temperature (PTAT) current source is proposed. The circuit has been designed and fabricated in a standard 180 nm CMOS technology. Measurements were performed on 10 prototypes in the temperature range of −40 to +85°C. The operating supply voltage of the proposed circuit is 850 mV ± 10%. The measured averaged temperature inaccuracy and the linearity of the proposed architecture is between +0.86/− 0.93°C and +0.69/−0.75%, respectively.Introduction: The on-chip temperature is rising with the increase in power density due to decrease in the feature size [1]. The increase in chip temperature directly affects the performance of mixed signal circuits. Methods such as dynamic voltage scaling [2] are quite common to address this problem in digital circuits, but they are not easily implementable with analogue blocks. Thus, to reduce temperature dependency in analogue blocks, a temperature dependence nullifier or an on-chip temperature sensor required for efficient dynamic thermal management [3]. Proportional to absolute temperature (PTAT) current sources are quite commonly used in mixed signal circuits to reduce thermal dependence. The classical method of implementing PTAT current sources requires the use of bipolar devices and resistors [4,5]. The low-power low-voltage PTAT current source implementation by using metal-oxide semiconductor field-effect transistors (MOSFETs) has been reported in [6][7][8]. The proposed PTAT current source is simple in implementation, is an extension of well-established circuit, consumes less power and is able to provide the moderate temperature accuracy required for on-chip temperature measurement applications.

A 40 nW CMOS-Based Temperature Sensor with Calibration Free Inaccuracy within ±0.6 °C

“…The BJT-based temperature sensors are widely accepted due to their accurate temperature sensing ability that can be below ±1 • C [4][5][6][7]. For all MOSFET-based implementations, a temperature accuracy less than ±2 • C has been achieved [8][9][10][11].…”