Research On The Chip Integration Technique Of Interface Circuit For High-performance Tunneling-magnetoresistance Sensors

Compared with Hall devices,anisotropic magnetoresistance and giant magnetoresistive magnetometer,the micro-tunneling magnetoresistance sensor(TMR)developed by magnetic multilayer material has many advantages,such as high sensitivity,high frequency response and good reliability.It is widely used in military and civil fields.The research on TMR micro-magnetometer integration has become one of the main direction of development.Therefore,it is of great significance to carry out the research on high-performance digital TMR interface chip integration.The high performance research of TMR micro-magnetometer has the following key problems: the background noise of the TMR micro-magnetometer is large and its minimum magnetic field resolution is affected.the large magnetic tunneling junction area in the TMR magnetometer can improve its sensitivity,but the temperature drift of the output is serious.The TMR micro-magnetometer interface circuit is still by the discrete device PCB integration,the problem of interface ASIC chip integration remains to be solved.In order to solve the corresponding problems,the noise characteristics and temperature characteristics of TMR sensitive structure are studied in this paper.The inte gration technology of TMR micro-magnetometer interface circuit chip is developed.The noise characteristics of TMR sensor are analyzed by the tunneling mechanism of TMR sensitive structure.The noise model of TMR sensitive structure is established.Therefore,the TMR sensitive structure noise spectrum is obtained.In the magnetic signal measurement of geomagnetic field,the signal is low frequency and weak magnetic signal.The noise caused by thermal excitation of magnetic domain wall is the main noise of the tunneling magnetoresistance sensor at low frequency.And the noise is not reduced by the high frequency modulation of conventional circuit method.Therefore,a magnetic shielding chopper modulation method is proposed in this paper.By analyzing the relationship between the amplitude,frequency of the chopper current and the sensitivity of the sensor,the optimum chopper current parameters are determined.The background noise of the TMR sensitive structure is reduced from 7.5n T/Hz1/2(@1Hz)to 0.15 n T/Hz1/2(@1Hz)by the magnetic shielding chopper modulation method,which proves the effectiveness of the method.In view of the temperature drift of TMR sensitive structure,the temperature characteristic of the magnetic tunneling junction is researched by the analysis of the electron spin polarization,and the relation between the sensitivity of the TMR sensor,the zero position and the temperature is obtained.The correctness of the model relationship is verified by the measurement of the temperature characteristic curve of the TMR sensitive structure.This paper proposes a temperature compensation scheme based on digital chip,which can effectively solve the problem of temperature drift in TMR.Based on the theoretical analysis and research of the noise and temperature characteristics of the TMR sensitive structure,a digital interface ASIC chip for the tunneling magnetoresistance sensor is designed.The chip mainly includes the low noise weak signal detection circuit and the high precision 4th-order Sigma-Delta ADC.By analyzing the non-ideal characteristics of the key modules of the interface circuit,the parameters in the circuit are optimized.With the help of Cadence simulation and 0.35?m four layer metal double polycrystal BCD process library,the layout and post simulation are completed,and the project batch is completed by the Shanghai Hua Hong standard 0.35?m CMOS process.Finally,the high precision test platform is built to test the interface ASIC chip and the TMR magnetometer.The test results show that the temperature drift coefficient of TMR micro-magnetometer before and after temperature compensation is reduced from-1100ppm/? to-117ppm/? at the range of-45~+85?.The measurement range of the magnetic field is ±100?T;the power consumption is 120 m W(threeaxis);the magnetic field resolution of the digital TMR magnetometer system is 0.26 n T/Hz1/2(@1Hz)and the nonlinear is 0.11%.The digital serial serial chip is integrated with the digital output back end of the designed TMR micromagnetometer prototype,and the real-time data communication with the PC machine can be completed,and the software Linear,zero-bias,temperature drift compensation and calibration functions is realized by the host computer software..The high performance TMR micro-magnetometer interface circuit chip integration is implemented.The theoretical research of the tunneling magnetoresistance sensor interface ASIC chip can provide important guiding significance for the technical progress of the high performance TMR micromagnetometer.It is of great significance to realize the integration and miniaturization of tunnel magnetores istive sensors.It has a broad application value in the field of high precision magnetic detection.