Design Of An Adjustable Current Reference

As a bridge between the digital world and the analog world, digital to analogconverter(DAC) is the key module of the signal processing system. The rapiddevelopment of processor and memory greatly improve the speed and the accuracy ofdigital signal processing systems, at the same time, the development puts forwardhigher requirements to the speed and accuracy of the DAC. In recent years, portabledevices developed rapidly, and the ability of endurance has become an importantindicator to evaluate this device, which makes the power requirements of the DAC areincreasingly demanding. Low-power high-speed and high-precision digital to analogconverter design has become one of the most important directions of IC design. Acurrent reference source with high performance is very important for high-speedhigh-precision low-power consume DAC.This article describes the technical indicators and the principles of the voltagebandgap reference, and then summarizes several structures of the bandgap reference. Atlast, this article points out the problems of the common bandgap reference. On this basis,this paper implements a current reference source which is adjustable in two directionsusing TSMC0.13μm1P8M sdandard CMOS process. This current reference includes avoltage bandgap reference, a votage to current converter and an adjustable currentgenerator. This paper includes the front end circuit design, layout design and test.According to the simulation results, when the current reference is78.69μA, themaximum forward and reverse regulation accuracy are1/1201and1/1003of thereference current, respectively; the maximum forward and reverse adjustment range are14.59%and14.93%of the reference current, respectively; the temperature coefficient ofthe bandgap reference is5.74ppm/℃,and the the temperature coefficient of thereference current is48.95ppm/℃; the test results shows that the output of the voltagebandgap reference is near1.182V, which meets the design requirements well, and thecircuit also works well in the DAC.