CMOS Mixed-signal Sensor Integrated Circuit Of Compatible Photo Quadrant Array And Magnetic Linear Array

Quadrant sensors based on silicon are now widely used in many fields, including the laser tracking, homing and collimation, the precision machine et al. Magnetic sensors based on semiconductor are also widely used in many areas, such as the measurement of the magnetic field, the read head of magnetic hard disk, the detection of non-magnetic signal, the automotive, contact less control and many ammeters. Traditional quadrant and magnetic sensors are not integrated with the CMOS signal processing circuits and it is impossible to realize the sensor system-on-chip and the smart sensor system.In this paper, the CMOS mixed-signal sensor IC is researched, which is combined with the photo quadrant arrayed sensor and magnetic linear arrayed sensor. It is consisted of active pixel quadrant array of P＋/N-well/P-substrate photodiodes, sector split-drain magnetic MOSFET linear array, correlated double sampling circuits, differential amplifier interface circuits and digital controlling circuits. In the quadrant array, the P＋/N-well/P-substrate photodiodes are used as the optical sensor cell. In the magnetic linear array, the sector magnetic split-drain MOSFETs (MAGFET) are used as the magnetic sensor cell. The CDS can be applied in the sensor signal sampling and noise-elimination for both P＋/N-well/P-substrate photodiodes and the sector MAGFETs. So the compatible signal processing circuits based on the CDS are designed for both the quadrant sensor IC and the magnetic sensor IC. In the design of photo quadrant sensor, the recombination of quadrant sensors and the CMOS image sensors shows great advantages, because the active pixel array can be used to obtain the coordinate and the shape information of targets. Contrasting with the traditional photodiode, the P＋/N-well/P-substrate photodiodes shows great advantages in the low dark current, the illuminance intensity sensing range and the photoelectric sensitivity. In the design of magnetic sensor IC, the two functioning modes of the sector MAGFETs are designed to realize the measurements of perpendicular magnetic field as well as the noise shaping: in the measurement functioning mode, the sector MAGFET are sensitive to the magnetic field, and in the magnetic-shielding functioning mode, the sector MAGFET works as the common MOSFET and is not sensitive to the magnetic field. In the design of magnetic signal processing circuits, the cross sampling and the synchronized sampling IC are designedd for the two functioning modes of the sector MAGFETs.The CMOS mixed signal sensor IC of compatible photo quadrants array and magnetic linear array are designed and fabricated in 0.6μm double metal double poly standard CMOS process. A 4×4 array of P＋/N-well/P-substrate photodiode and the 4×1 linear array of sector MAGFETs are designed. The pixel size of P＋/N-well/P-substrate photodiode is 100μam×100μm. The channel length of the sector MAGFET is 48μm, with the source semidiameter of 10μm and the source angle of 90°.The measurement results of the chip are as follows. The P+/N-well/P-subst0ate photodiode can obtain target information with illuminance intensity in the range of 0.011x-98,0001x, with the sensor photoelectric sensitivity is 25 V/Ix·s. When the method of double scanning is used, the photoelectric dynamic range is 139.8dB.The sensor sensitivity of 3.63% of the sector MAGFET is obtained, which is higher than that rectangular MAGFET reported (3.0%). The cross sampling circuits and the synchronized sampling circuits realize the measurement of the magnetic field, as well as the noise-shaping of the magnetic sensor signals. The cross sampling circuit take the advantage in the matching of the two functioning modes and the simple circuit structure, and the disadvantage is that the noise in the holding time of sensor signal, which can't be eliminated. The synchronized sampling circuits can eliminate the noise in the holding time with relative complex circuits and the low matching of the two functioning modes of sector MAGFET. At the frequency of 20 KHz, the sensitivity of the sector MAGFET IC reaches 2.62V/T, and the magnetic field ranging from 0.01T to 0.5T can be detected.The double functional sensor system can be used as a short distance(magnetic sensing) and a long distance(photo sensing) displacement sensor and also be used in intelligent reorganization system.