The Research And Design Of A Curvature Compensation Bandgap Reference With Thermal Protection Circuit

Reference voltage sources and reference current sources are an essential part of many analog and digital electronic systems, such as applications on switch power supply management (SPSM) ICs, LED drivers and D/A, A/D converters et al. The reference sources are much more accurate and steady than the common sources. It should supply an output voltage with very low temperature and process corners coefficient, and should be insensitive to supply voltage. The performance of reference sources determines directly the steady of systems. So the reference source with excellent performance is the crucial and basic demand.Portable electronic products have become increasingly popular. These products are high integration, small size characteristics. As the battery capacity assurance modules- SPSM chips, their performances also need to constantly improve, mainly reflected in the reduced volume of module, and also necessary to maintain its carrying capacity the same. With the switch operating frequency increasing, higher requirements are demanded on the internal integrated voltage reference's PSRR, anti-noise performance and temperature stability. As a result of transistors surge in per unit area, thermal agglomeration problems highlighted, over-temperature protection has become a problem that can not be ignored.In this paper, we analyzed a variety of factors affecting the accuracy and temperature compensation strategies. From the device selection and structural optimization considerations, we proposed a high-performance voltage reference with OTP which is based on Brokaw bandgap core.On the basis of structure analysis, we optimized bandgap reference frequency response and improved the PSRR (power supply rejection ratio) performances. High-temperature curvature compensation circuit structure is simple and effective. Used piecewise linear compensation method at high temperature can give a direct adjustment to the temperature curve of output voltage, and effectively improve the temperature stability. Over-temperature protection function has implemented by VBE voltage negative temperature coefficient of NPN-type transistor and the size of resistance accessed in NPN base. To set temperature thresholds, the added pre-turn-on design makes the overheating and security turn-on point with high sensitivity and output control signals to establish quickly. The simulation results for this circuit using Hspice show that the temperature coefficient is about 20.2ppm/℃and the output reference voltage is 1.2±0.005V, 2.5V-5.5V supply voltage. The typical PSRR(Power Supply Rejection Rate) is 75.6dB. The threshold temperatures of the internal integrated thermal shutdown circuit with hysteresis are 160℃when OTP shutdown and 140℃when safely turn-on. Designed hysteresis margin can prevent thermal oscillation perfectly.