A Bandgap Voltage Reference With Temperature Curvature Compensation And High Crossover Frequency

Along with the continuous developing of portable applications, the size of portable electronic equipment is getting smaller and smaller. As the main power supply modules of the portable equipment, the space of switching power supply modulator needs to be reduced. For this reason, a higher switching frequency of the switching power supply modulator is required. This gives its internal voltage reference macro a higher frequency power supply rejection ratio (PSRR) performance demand.In addition to power supply rejection ratio, the temperature stability of the output voltage reference is also an important performance specification. Currently, many second-order temperature curvature compensation bandgap references are realized with very complex structure. It may result a larger offset voltage from device mismatch. This offset voltage causes the output voltage deviate from the original typical value. Beside the temperature coefficient of the reference voltage will be affected by the temperature coefficient of the offset, maybe even worse than compensated before.In view of the two questions above, this paper analyses and compares two different bandgap reference structures. After that the main structure of the new bandgap reference is determined by combined the respective advantages of the two structures above, research on device selection and structure optimization is following. There are mainly three improvement made in the new bandgap. First, second-order temperature curvature compensation is received by taking a resistance with negative temperature coefficient. Second, based on the Brokaw bandgap reference structure, an additional NPN transistor and resistor are used to directly adjust the temperature coefficient of output voltage in high temperature region. Third, based on the small-signal analysis of the Brokaw structure, a new method which introduces a zero into the Brokaw structure is proposed. This zero effectively improves the crossover frequency of the bandgap reference loop, and then optimizes the high frequency PSRR performance of new bandgap reference. Each of the improvement has been simulated to prove its effectiveness.The performance of the designed bandgap reference is derived from Hspice simulation. The simulation results show that the temperature coefficient and power supply rejection ratio performance of the new bandgap reference structure have been optimized to achieve the desired results.