A 5-μA Low Power Over-Temperature Protection Circuit With High Voltage and Process Stabilities for Line Driver in PLC Applications

This brief introduces a over-temperature protection (OTP) circuit used in line driver chip for PLC applications. For the limitations of the BJT process, the proposed circuit adopts a current distribution structure with a positive loop to realize state switching if the temperature exceeds the threshold or recovers, instead of the traditional structures with integrated comparators in the CMOS process. The method minimizes quiescent current (IQ) and transistor consumptions of the circuit. In addition, due to no comparator exists, there is no need for reference voltage, so that the process and voltage stabilities of the circuit are improved. The OTP circuit is implemented by SOI-BJT process, and relies on a line driver chip for verification. The module consumes 5- $\mu A$ IQ, which only accounts for 0.02% of the whole chip. The measured maximum temperature drift of the circuit is $0.167\,^{\circ }\mathrm {C/V}$ under the power supply voltage range of 6-30V, and the average hysteretic temperature drift of 6 random sampled chips is $0.15\,^{\circ }\mathrm {C}$ .