Design Of Voltage Reference For TopMetal2-Chip

TopMetal2-is another pixel sensor chip after TopMetal which is only designed by our group.The theory is similar with TopMetal’s,namely that using the metal exposed to the air to collect charge in the air and then convert the chage into voltage signal which could be readout.Reference voltage source is one of the core circuits for all analog system or digital system.So it is an essential part of the TopMetal2-chip.The stability of the whole system depends on the stability of Voltage Reference source.Firstly,the paper describes the development and research status of reference source in the integrated circuit,and then analysis the basic principles and the performance of refernce source.The paper focus on the CMOS bandgap reference voltage source which is applied to TopMetal2-chip,including the design of start-up circuit,core circuit,operational amplifier and buffer stage circuit.The circuit,with the conventional CMOS bandgap reference structure,takes the advantage the operational amplifiers to keep the stability of voltage,at the same time,simple and effective start-up circuit offers the normal operating state.Finally,the design of output buffer improves the driving capability of the circuit.Based on xfab0.35um process and3.3V supply voltage,the bandgap show good performance.In the pre-simulation,the temperature coefficient is17.3ppm/℃and the PSRR(Power Supply Rejection Ratio) is107.4dB.After the layout is finished, temperature coefficient is16.8ppm/℃and the PSRR is122.5dB which meet the design requirments.