The Analysis And Design Of A High Performance Bandgap Reference

The Bandgap Reference is an important module of Power management circuit, A/D Converter, D/A Converter and the other analog circuits or Mixed-signal circuits. The so-called "reference" means that the voltage or the current has higher accuracy and stability relative to the power in general. The bandgap reference voltage or current have nothing to do with the supply voltage,temperature and process variations.It's performance has a direct impact on accuracy and stability of the entire circuit. As the prompt improvement of the SOC's integration level and the rapid development of semiconductor manufacturing processes, Mobile phones, laptop computers, MP3, digital cameras and other portable electronic devices have developed rapidly. When this kind of products develop towards multimedia, high quality and versatility, in the mean while, their battery life and small size, set higher requirements. To meet these requirements, they need an efficient power management chip, which can adjust the the supply voltage of each module real-time according to the system state, reduce power consumption as much as possible, to improve the efficiency of the system, reduce the volume of products and the cost of production. But the Bandgap Reference is the fundamental of the power management IC, so the design of a high performance bandgap reference has a very important practical significance. My bandgap reference designed in this paper can be widely used in a variety of power management chip.In the second chapter, we mentioned that the the main parameters of Bandgap Reference are the temperature coefficient, power supply rejection ratio, load regulation and power consumption. Because there are certain constraints between the various parameters, it is difficult to design a Bandgap Reference which properties are all excellent. In this paper, we optimize the performance according to the two parameters, power dissipation and power supply rejection, and have completed the circuit design process, including the circuit analysis and design, pre-simulate, the layout design and verification and post-simulate.This design uses the 0.13um standard CMOS process. We use Virtuosio editor to get the circuit schematic and layout, and use the HspiceD to simulate, use Calibre which provided by Mentor to verify the layout. The main design's specifications are as follows: Input supply voltage range from 1.5V to 5.5V; At low frequency, the PSRR is higher than 80dB, and no less than 30dB in the 40kHz; The total quiescent current is less than 10uA.In the design of Bandgap Reference, the difficulties are: How to minimize the quiescent current of each branch of the circuit, so that the total quiescent current to maintain the design goal of less than 10uA; As the limit of technology, when the supply voltage is minimum 1.5V, the voltage margin is not enough, so that the error amplifier does not work whatever N or P control input; Since the limit of static power, how to improve PSRR without increasing the complexity of the circuit, to achieve the design targets, etc.This design is the improvement of the Kujik Bandgap Reference structure, it is consist of the start circuit, bias circuit, error amplifier and the core of the bandgap reference. To solve the above difficulties, we made the following main optimization measures: When the supply voltage is 1.5V, as the transistor's base-emitter voltage is about 0.68V, the P control input op amp is not working properly, therefore, N control input folded cascade amplifier is adopted, at the same time, we use two resistances between the input of amplifier and the transistor to improve the input voltage of the NMOS differential pair; In order to increase the load capacity of the circuit, we change the two mirror PMOS in the traditional circuit into one; In order to improve PSRR, simultaneously, without significantly increase the total quiescent current of the entire circuit, a subtractor has introducted between the main circuit and the error amplifier, etc.While the supply voltage is the typical value 3.5V, the load resistance is 200kΩ, we have simulated the circuit of the various combinations of the corners of transistors and resistors. The results show that, at low frequencies, the PSRR is about 85dB, at 40kHz is about 30dB. When the supply voltage changes from 1.5V to 5.5V, the minimum quiescent current consumption of the whole circuit is about 5.1uA, the maximum is only 8.3uA. When the temperature ranges from -50°C to 120°C , the lowest temperature coefficient is about 17.4ppm /°C . In addition, it also has good line regulation, when the power supply voltage range from 1.5V to 5.5V, in the combin- ation of different corners, the maximum change of output voltage is 179uV, while the minimum is about 133uV. The simulation result of pre-simulation and post-simulation are almost equal. Almost achieved the low power dissipation and high PSRR of the design goals.