The Design Of Resistive-type Touch Screen Controller

With the great improvement in microelectronics and computer technology, morecomputerized devices now contain Touch-screen technology. Touchscreens arebecoming more and more popular today in the electronic field and you can see it inalmost every latest gadget. Even though Some people might think that Touch-screentechnology is just more of a luxury than a necessity, touchscreens are becoming moreand more commonplace every day.They’ve been used very often especially onportable electronic products. Most importantly, they have replaced the traditionalkeyboard and become the most popular input device for embedded computer systems.A touchscreen can detect the presence and any location of a touch within the displayarea. One of its main attributes is that it enables one to interact directly with what isdisplayed, rather than indirectly with a pointer controlled by a mouse or touchpad.Very interesting while attractive. There are a variety of touchscreen technologies thathave different methods of sensing touch. Of all those technologies, resistive-typetouch is used in restaurants, factories and hospitals due to its high resistance to liquidsand contaminants. A major benefit of resistive-type touch technology is its low cost.The controller chip is the most important part of a resistive-type touchscreen.Aquickly rising demand for touch screen devices will trickle down to a equally fastincreasing demand for touch controller and triple that market in future.So I’m gonna design a special kind of touchscreen controller on the basis of the4-wire touch screen controller theory.The whole controller contains a ADC（ananalog-to-digital converter） module, a temperature measurement module, a batterymeasure module, six channel module, a digital control module and a interal referencemodule. The core of this4-wire touch screen controller is a12-bit ADC. My maintask is to design a high-resolution and low-power ADC on a very small area. I’vechose the most qualified12-Bit SAR ADC as the core because of the fast conversionspeed, high precision and its low power consumption. The speed of the successiveapproximation ADC conversion is very fast. And it got high precision and lowpower consumption. So I uesd the12-bit successive approximation ADC chip as the core. My SAR ADC contains a switched-capacitor comparator which can reducepower consumption by clock control. This IP has an on-chip2.5V bandgap reference.And the reference can also be powered down when not used to conserve power. I’vedesigned a bandgap reference as an internal voltage reference source on the internalbenchmark module. As my design, the chip can also be carried out in the internalreference and external reference switch to minimize the role of power consumption,and the resolution of the entire chip is high enough while maintaining low powerconsumption.My design is based on the world’s leading Taiwan Semiconductor ManufacturingCompany (TSMC)65nm technology. The first image representation of the circuit hascompleted in the Cadence environment. Then I used the Synopsys’ Hspice software tosimulate the circuit. Then I completed the design of the layout and using the virtuosoin the Cadence environment and uesd the Calibre for validation. During the wholedesign I’ve taken full advantage of each integrated circuit design software, whichgreatly improved the efficiency of the device and minimized the design bias that mayexist in my work. All the modules turned out to be very good during the simulation.The controller has achieved high precision, low power consumption and very smallarea. I truly believe that my design is gonna be widely used in touchscreen productssomeday.