A 4-Transistor Monolithic Solution to Highly Linear On-Chip Temperature Sensing in GaN Power Integrated Circuits
Ang Li, Yi Shen, Ziqian Li, Fan Li, Ruize Sun, Ivona Z. Mitrović, Huiqing Wen, Sang Lam, Wen Liu
Abstract
We report the monolithic realization of on-chip temperature sensing design using four transistors (4T) in gallium nitride (GaN) technology. The temperature sensor consists of a voltage reference and a logic inverter, both of which are built from enhancement-mode (E-mode) and depletion-mode (D-mode) metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs). The temperature-insensitive voltage reference outputs a very stable voltage as the input of the logic inverter, which exhibits good temperature dependence in its voltage transfer characteristics. As the temperature varies from 25 to 250 °C, the output voltage of the logic inverter changes linearly. By configuring the active-load D-mode transistor as a two-dimensional electron gas (2DEG) resistor in the logic inverter, the temperature sensing solution is improved further, showing stable sensing output, higher sensitivity (31.28 mV/°C), better linearity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{R}^{{2}}$ </tex-math></inline-formula> = 0.995) and smaller error (±2.74 °C). This demonstrates a compact monolithic sensor for monitoring the on-chip temperature of GaN power integrated circuits (ICs) for protection and control.