The Research And Design Of Bandgap Reference With Over Temperature Protection

A lot of modules in the analog and digital integrated circuit (IC) need reference voltages and stable bias currents. So reference circuits are widely used in these systems. The reference designed must meet the following requirements, low temperature coefficient (TC), high power supply rejection ratio (PSRR) and low relativity to parameters such as process corners. Reference with excellent performance plays a important role in the function realization of many modules.Reference is applied in various kinds of ICs, such as DC-DC、AC-DC and A/D or D/A chips. The products above are of high integration level and operate in high frequency. So the reference must have good power supply rejection capacity and anti-noise capacity besides precision. The bandgap reference (BGR) has high PSRR and low TC, so it’s a widely used topology in the reference. The temperature of the system changes with the load. When the temperature exceeds the safe threshold, system needs to shutdown the modules. When the system temperature exceeds the set value, the over temperature protection (OTP) will be triggered and the voltage divider ratio of resistors changes. Thus a hysteresis is generated.In this paper, device selection and circuit architecture are studied based on the comparison of different reference architecture and temperature compensation schemes. A low temperature drift BGR with curvature-correction is designed base on OKI 0.5μm BCD process. The BGR is a Brokaw reference with high order compensation current. The reference current is generated from the zero TC voltage in simple circuit. The simulation verification of the circuit designed in this paper is conducted via Hspice software. Simulation result shows that, the TC of reference voltage is merely 3.9ppm/℃, the reference current changes 0.2% from -40℃～150℃. When power supply voltage varies from 3V to 6V, the reference voltage fluctuation is 562μV, reference current fluctuation is 2.2nA, the PSRR in low frequency (below 10kHz) is up to -76dB.Simulation shows that, the temperature performance of the reference designed in this paper is upgraded obviously. The low frequency PSRR is good, the reference structure is simple and set up time is relatively short.