Research On Wide Range Co-Based Multi-Layer Spin Sensor And High Precision Interface ASIC

Spin electronics is a subject that studies the combination of electron spin and electronics,and it has become a hot research field in condensed matter physics in recent years.Spin sensors based on Preparation of spin electronic materials with high thermal stability,radiation resistance,high precision,low power consumption and other advantages,widely used in national economy,national defense,science and technology,health and other fields.Future spin sensor systems are moving towards high sensitivity,wide dynamic range,low power consumption,and integrated intelligent direction development.Spintronic materials and standard CMOS process has good compatibility.Therefore,high performance and new type spin sensor development,and high precision sensor interface ASIC circuit have important research significance and practical value.Co based multilayers with huge effect of spin orbit coupling and easy controlling of magnetic anisotropy,become the material of choice for next generation spin sensors.This paper studied the anomalous Hall effect(AHE)of Co based wide field sensor materials and thin film temperature sensor materials.Firstly,Co/Ni?Co/Pt multilayer films were prepared by magnetron sputtering,the magnetic is strongly dependent on the thickness of Co,Ni and Pt thickness and number of bilayers.Through preparation of appropriate thickness,number of cycles thin film samples to enhance the Anomalous Hall effect,improve the Hall resistance loop linearity and expansion work field dynamic range,We finally found applicable to the strong magnetic field of the anomalous Hall sensor materials.Then we studied the temperature properties of Co/Pt and Co/Ni materials.The magnetic properties of the samples shows strong temperature dependence.The perpendicular anisotropy and anomalous Hall resistivity at zero field decrease with increasing temperature.When the temperature is higher than the spin reorientation temperature,the materials of the anomalous Hall resistivity values became constant.According to this characteristic,we can prepare suitable film to make linear film temperature sensors and the specific temperature switch sensors.For spin sensor interface specific application as well as the small size,low powerconsumption demand,this paper presents a custom designed sensor interface ASIC,the signal conditioning circuit and the analog-to-digital conversion circuit are integrated in a single chip.Conditioning circuit uses instrumentation amplifier,which is the ideal choice for sensor signal amplification.Its unique structure makes it with high common mode rejection ratio,high input impedance,low noise,low linearity error,low offset drift.In order to improve the input common mode range of instrumentation amplifier,front-end amplifier using complementary rail to rail operational amplifier is realized by using the improved chopper nesting adjustable gain instrumentation amplifier.Compared to the traditional nested chopper amplifier,not only the gain of the op amp is adjustable,the structure of the circuit has higher linearity,and the residual offset is smaller.Spin sensors' output signal is very weak and sensitive to the low frequency noise.While the traditional ?? ADC with dynamic memory,that will introduce a larger offset voltage,can not meet the needs of high precision sensor.This paper uses incremental ??ADC,which can overcome the shortcomings of the traditional ?? ADC.Firstly,the basic principle of incremental ?? ADC is described in detail,and the time domain and frequency domain analysis of first order,two order and general high order incremental ??ADC are carried out.Secondly,according to the requirements of incremental ?? ADC,modulator topology,bits of quantizer,and modulator parameters were designed.The non-idealities of ?? ADC will greatly affect the modulator performance,so it's necessary to make a systematic analysis on finite gain of the integrator,limited bandwidth and slew rate,clock jitter,sampling noise and switching nonlinear.Modeling these non ideal factors by using MATLAB provide a theoretical reference for the actual modulator performance.The circuit level design of incremental ?? ADC is based on the 3 order single bit quantization.In order to suppress the noise of the first integrator,a gain boosted folded cascode operational transconductance amplifier with very high DC gain and unity gain bandwidth was used.At the same time,the correlated double sampling technology is introduced,which effectively eliminates the offset voltage,l/f noise and the dynamic offset voltage due to the limited gain.Quantizer in the comparator using improved class AB latched structure,effectively isolates the kickback noise and improves the speed of the comparator.Test results show that the output signal to noise ratio is 86.8dB,the effective numberis 14,DNL and INL are 0.41,0.53,respectly,both less than 1LSB.The chip was taped out with CSMC 0.18?m CMOS process,the total current is 11.92 mA,and the offset voltage is only 0.072 mV.Then the AHE sensor measurement system is constructed by the interface ASIC and AHE sensor which we prepared.The test results show that the system can realize the sensing of the magnetic field signal,signal modulation and analog to digital conversion.