Embedded Temperature Sensor for Multilevel Current LED Driver

In this paper, we propose an embedded temperature sensor for the control of light emitting diode (LED) driving current, providing linear sensing, in which the output of the analog voltage corresponds to the current temperature. Sensing levels are truncated to four regions: 1) 120°C; 2) 140°C; 3) 160°C; and 4) 180°C. Thus, an increase in temperature is met with a corresponding drop in driving current to avoid burning the chip. A test chip was fabricated in using the TSMC 0.25-um CMOS process based on high-voltage mixed signals, in which two-channel LED drivers were embedded with two temperature sensors. The chip proved highly effective in all tests.