Design Of High Precision Rail-To-Rail R2R DAC Adaptable To Sensor Interface

Nowadays, with the extraordinarily rapid development of the automotive and electronic industry, smart car becomes a hot spot. And intelligent in the car is mainly accomplished by automotive electronic equipment. Public pay more and more attention to the safety and comfort of automobile. Therefore, there has been a great demand for engine electronic control system with lower power and high precision. As is known to all, DAC is the core module of engine electronic control system circuit. With this background, this paper focuses on research and design of high precision rail-to-rail R2R DAC adaptable to automobile engine sensor interface.In this paper, the theoretical of DAC has been deeply studied. There are several common structures of DAC known as current-steering DAC, string resistance DAC,charge-redistribution DAC and R2R ladder DAC. This paper analyses and summarizes DAC features of different structures. R2R ladder DAC has the advantages of simple structure, lower power, small area and high resolution. According to the requirement of the automobile engine sensor interface application, the resolution is 10 bit and setup time is less than 10 us, so the DAC in this paper is realized with R-2R architecture which can be fully satisfied the requirement. Current spike problem exist in traditional circuit is solved by no overlapping clock circuit; INL and DNL are reduced by the switch array matching technique and the optimization of rail to rail output amplifier also reduced offset errors and setup time. Through the LDO provides a stable reference voltage. Moreover, this DAC has different operation modes and frequencies to realize low power implementation.The R2R DAC has been implemented with AMS 0.35?m 5V Mix Signal 1P5 M process. The INL is ±0.32 LSB, and DNL is ±0.45 LSB. This expresses the DAC has a high precision. The rail to rail output range is 4.6mV-4.992 V, and setup time is optimized to 1.21?s. The layout area is 400?m × 360?m. The parameters meet the specification requirement and satisfy the automobile engine sensor interface requirement for high precision and rail to rail output.