Design Of Adc Applied To Hall Sensor Readout Circuit

From 20th century,with the rapid improvement of integrated circuit technology,designers integrated susceptor elements with signal conditioning circuit formulating early sensor.Sensors are the first link in making automatic detection and automatic control come true,they are becoming increasingly miniature,digitized,intelligent,multipurpose and systematic.At present,various types of sensors have been applied to all aspects of life,such as temperature sensor DS18B20,widely used in granaries,deep wells and aviation,monitoring temperature variation all the time.Some other sensors like smoke sensor MQ-2 used in fire alarm system,alcohol sensor MQ-3 applied in traffic enforcement.Among them,with the advantages of small size,high sensitivity,strong diamagnetic disturbance and so on,the Hall sensor has occupied an important market share and become the world's third-ranked sensor products.In view of the wide application of Hall sensors,the processing and research of its output signal has become a key problem.Based on this,in this paper the post-processing circuit will be studied.Hall readout circuits mainly include variable gain low noise amplifiers and analog-to-digital-converter(ADC).Analog-to-digital converts work as interface circuit in sensor readout circuit,their performance directly affect readout signals' quality.Successive approximation register type analog-to-digital convert(SAR ADC)is commonly used in structures with sampling rates below 5MHz,it has the advantages of high resolution,low power consumption,small size,etc.These advantages enable SAR ADC to be used in a wide range of applications,such as portable battery-powered instruments,wearable devices,industrial control and data signal collectors,etc.With the development of integrated circuits technology,power consumption problems are increasingly prominent.As a typical representative of low-power analog-to-digital convert,it plays an important role.This article has mainly studied in low-frequency sensor(working frequency less than 1MHz),considering from two aspects:1)In order to improve precision,designed a bootstrapped switch and a comparator.Parasitic compensation capacitors were add into the circuit for reducing influences from parasitic capacitors;2)From the perspective of low power consumption,segment capacitor structure was applied in this design,in this new structure we used the capacitor plus plate sampling structure,one-way switch capacitor array.Compared with traditional structure,this new SAR ADC has smaller area and lower consumption.All the analog and digital parts in this paper are made of full custom design,it is convenient for optimizing later.This design use of SMIC 0.18um CMOS technology,designed a 12bit,1MHz sampling-rate SAR ADC chip,the simulation analysis was performed on the Cadence platform,simulation results show that in the 1MHz sampling rate the whole circuit effective number of bit is 11bit,the chip area is 0.401mm2,the power consumption is 0.27mW.