The Research And Implementation Of Capacitive Touch Sensor Based On Third-order Sigma-deltaADC

AS the technology of microelectronics and microprocessor develops, the electronic products with touch technical has penetrated into many aspects in our daily life.compared with the traditional mechanical button interface, It(such as touch switch) is thin, cheap, fashionable appea rance and so on. therefore,touch technology becomes more and more popular in our life, such as touch keys, touch slider, touch panel, touch screen, which have been accepted widely. Due to make use of noise shaping along with over sampling and digital decimation filter technique as well as using the switched capacitor circuit, Sigma-delta ADC relax the accuracy of the analog circuit element relative to the low speed ADC, It is easy to achieve the required signal to noise ratio and resolution.It is suitable for low frequency and high precision situation. Due to the ADC performance has a direct influence on the accuracy which the touch sensor can reach, this paper discusses sigma-delta ADC based on touch sensor in detail The behavior level simulation model o f sigma-delta modulator based on touch sensor is established with matlab2012 a. which analyzed the main non ideal factors.It makes use of cadence virtuoso and spectre tools to designe and simulate and verificate for the related circuit. The simulation res ults show that the resolution of the touch sensor can reach 18 bits, The senor has rapid response speed, in addition,it can make reaction for non-contact induction.It can also be used in the situation where deep penetration should be required. The design of amplifiers the touch sensor are programmable, whicth would be able to magnify the small difference changes of voltage arross the capacitance in the process of fingers approch to the capacitor touch sensor, whitch increases the sensitivity of the sensor.The touch senor can choose different magnification and different sensitivity according to the specific application environment.therefore, the touch sensor has a wide applicability. The op amp and comparator and some other analog modules are designed with low power technology. If the sensor would be not touched for a long time. It would go into the sleep mode, when it be touched,the system can quickly be awaken to enter the fast mode.