Oversampling Successive Approximation Technique for MEMS Differential Capacitive Sensor

This paper proposed an over sampling successive approximation (OSSA) technique to build switched-capacitor capacitance-to-voltage convertor (SC-CVC) for readout circuit of MEMS differential capacitive sensor. The readout circuit employing the OSSA technique has significantly improved resistance to common-mode parasitic capacitance of the input terminal of the readout circuit. In the OSSA readout circuit, there are 5 main non-ideal characteristics: holding error, recovery degradation, increment degradation, rise-edge degradation and charge injection which reduce the accuracy and the settling time of the circuit. These problems are explained in detail and their solutions are given in the paper. The OSSA readout circuit is fabricated in a commercial 0.18um BCD process. To show the improvement evidently, a reported traditional readout circuit is also reproduced and fabricated using the same process. Compared with the traditional readout circuit, the proposed readout circuit reduces the affect of common-mode parasitic capacitance on the accuracy of SC-CVC by more than 23.8 dB, reduces power dissipation by 69.3%, and reduces die area by 50%

Design and Fabricate the High Sensitivity and Stable Optocoupling Sensor

A novel photodetector array (PD) and the high sensitivity transimpedance amplifier (TIA) were designed and fabricated for predicting response time based on the optocoupling sensor, implemented in a standard 0.35 m BCD technology. Based on response time equivalents and the architecture of the optocoupling sensor the response time of the PD were detailed analyzed. The circuit structure and the adjustable gain theory of the TIA module was clarified detailed. At a wavelength of 840 nm, from -25 C to 125 C, the simulation results showed that the PD has a high-speed and stable capability. The test results confirm the response time of the whole sensor is 205 ns and 153 ns and the response time would not change with the variation of the temperature

Symmetrical Structure Strong Drive Capability Optocoupler Sensor

A novel de-noising and strong driving current optocoupler sensor was designed and implemented in a standard 0.35 um BCD technology. A symmetrical structure of the photo detector array (PD) and the transimpedance amplifier (TIA) could eliminate the noise feedback from the substrate. The logic control module and the push-pull driver circuit could provide more than 3 A under the voltage lockout circuit (UVLO) protection. Experimental results confirmed that when the power supply is 30 V and the working temperature is 25 C, the sensor forward peak current is 2.8 A and the negative peak drive current is 2.5A

Capacitive Touch Panel with Low Sensitivity to Water Drop employing Mutual-coupling Electrical Field Shaping Technique

This paper proposes a novel method to reduce the water interference on the touch panel based on mutual-capacitance sensing in human finger detection. As the height of a finger (height >10 mm) is far larger than that of a water-drop (height 10 mm) and low in the low-height space (height <1 mm), the sensing cell can be designed to distinguish the finger from the water-drop. To achieve this density distribution of the electrical field, the mutual-coupling electrical field shaping (MEFS) technique is employed to build the sensing cell. The drawback of the MEFS sensing cell is large parasitic capacitance, which can be overcome by a readout IC with low sensitivity to parasitic capacitance. Experiments show that the output of the IC with the MEFS sensing cell is 1.11 V when the sensing cell is touched by the water-drop and 1.23 V when the sensing cell is touched by the finger, respectively. In contrast, the output of the IC with the traditional sensing cell is 1.32 and 1.33 V when the sensing cell is touched by the water-drop and the finger, respectively. This demonstrates that the MEFS sensing cell can better distinguish the finger from the water-drop than the traditional sensing cell does.National Research Foundation (NRF)Accepted versionThis work was supported in part by the National Natural Science Foundation of China (NSFC) under Grant 61771363, in part by the China Scholarship Council (CSC) under Grant 201706960042, and in part by the National Research Foundation of Singapore under Grant NRF-CRP11-2012-01