Low-voltage Low-power Bandgap Reference Research Under Nanometer CMOS Process

With the development of CMOS process technology, the critical dimensions keepscaling down. Cost, power consumption and supply voltage of integrated circuit arereduced significantly. Low-voltage low-power integrated circuit trend is promoted byNanometer process, especially in digital integrated circuit. Bandgap reference circuit isa basic part of the system of analog circuits and mixed circuit system. Low voltage lowpower design of bandgap reference is great significance to integrated circuitdevelopment.Firstly, the challenges faced by the reference design under nanometer COMSprocess and features of the bandgap reference are introduced. By comparing with thetraditional low-voltage low-power bandgap reference circuit structure, and combiningwith the characteristics of nanometer process, the main considerations of bandgapreference design are summarized.Then, the threshold voltage of MOS devices and its temperature characteristics areelaborated by combining with the device structure of nanometer process, thecurrent-voltage characteristics of the MOS devices are described, the characteristics ofthe MOS devices conductivity which operated in the sub-threshold region. A currentsource circuit with constant positive temperature coefficient and a current source withsecond-order temperature characteristic are deduced. And then a reference circuit basedon the MOS device structure which achieves second-order temperature compensation iscome out.Then, based on conductive characteristics and threshold voltage characteristics ofMOS device a novel structure bandgap reference circuit is designed and simulated. Thesimulation results show that the output voltage of the circuit is0.5V, the temperaturecoefficient of the circuit of2.3ppm/℃in the TT process corners is achieved, in allprocess corners it is better than40ppm/℃. From the simulation waveformssecond-order temperature compensation can be seen. Power supply rejectionperformance of reference circuit is better than-50dB, the supply voltage of bandgapreference circuit range from0.9V to1.5V. Finally, the differences of layout of traditional process and nanometer process areanalyzed. STI and WPE effects and solutions on the layout of the low-voltagelow-power bandgap reference circuit are analyzed. And30chips are tested, and the testresults show that the output voltage of reference relative to typical values range from-7.2%to12.6%. PSRR of the reference is better than-40dB, the temperatureperformance of the reference is better than100ppm/℃, second-order temperaturecompensation can be seen from the test waveform.The simulation and test results confirmed that the structure of low-voltagelow-power bandgap reference design is feasible and some reference value on design ofbandgap reference.