Research On Interface ASIC Of Micro Gyroscope With Ball-disc Rotor

The micro gyroscope with ball-disc rotor has superiority in aspects of magnetic suspension stability and rotor speed,and it has grabbed serious attention and become a hot research topic in the field of micro gyroscope.To further improve the performance and integration of the micro gyroscope with ball-disc rotor,it is necessary to carry out the integration of interface circuit.ASIC(Application Specific Integrated Circuit,ASIC)technology plays an important role in improving the performance and integration of the sensor interface circuit.Research on interface ASIC for the structure is an important means to improve the performance and integration of the device.Several key problems need to be solved in gyroscope with ball-disc rotor interface ASIC design.These key problems include the electrical characteristics of the sensitive structure,the noise characteristics of the detection system and the new detection method.In order to solve these key problems,the following investigations were conducted in this paper.Firstly,overall scheme for interface ASIC of micro gyroscope with ball-disc rotor was designed.The interface ASIC construction requires integrated circuit simulation tools aided design,but equivalent electrical model for the gyroscope with ball-disc rotor interface hasn’t been promoted for the present.The nonideal factors of the micro gyroscope with ball-disc rotor were analyzed,and the equivalent electrical model was established by the method of energy conservation and parameter equivalent.The model was applied to the system simulation of interface ASIC.The simulation results and the measured results of interface ASIC system are consistent with the trends of the response.Secondly,system noise model for interface ASIC of the gyroscope with the ball-disc rotor was also constructed.The system noise model contains the micro gyroscope mechanical noise,the driving disturbance and the circuit noise,which be applied for interface ASIC topology and device parameter designs.However,the existing system noise model doesn’t consider the effect of the nonideal factors as described above.The relationship between mechanical noise and structural parameters of the detection circuit were analyzed.Quantitative research on circuit noise and drive disturbance were given,and thus optimal interface ASIC topology structure was promoted.The experimental results show that the optimized detection circuit can effectively reduce the system noise level based on the theoretical analysis of the system noise model.Thirdly,detection accuracy of micro gyroscope with ball-disc rotor is limited because of the cross coupling and multi frequency aliasing problems.In order to solve the signal cross coupling and aliasing phenomenon in the angular velocity sensitive structure,one high-accuracy capacitance measurement method of feeble capacitance with frequency division and time division multiplexing for interface ASIC was proposed.The simulation results showed that frequency division and time division multiplexing detecting method would degrade the signal cross coupling by one order of magnitude.Finally,the chip of micro gyroscope with ball-disc rotor interface ASIC with with frequency division and time division multiplexing was manufactured on 0.5 μm high voltage CMOS(Complementary Metal Oxide Semiconductor,CMOS)process.The experimental results of chip show that the capacitance relative resolution is 1×10-8 and the nonlinear error is 0.02%.Test on the matching chip and gyroscope with ball-disc rotor revealed that the system noise is 0.003 o/s/Hz1/2 and nonlinear error is 0.05%.