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ADI 公司的AD7879/AD7889是带同步串行接口和低导通电阻开关的 12位SAR ADC,可以驱动4线电阻型触摸屏.单电源1.6V-3.6V工作,吞吐量速率高达105kSPS.主要用于PDA,智能手持设备,触摸屏监督器,POS终端,医疗设备和手机.本京电港论坛文章先容AD7879/AD7889主要特点, 功能方框架图, 模拟输入架构框架图, 典范应用电路原理图纸和AD7879评估板主要特点与电路原理图纸. The AD7879/AD7889 are 12-bit successive approximation analog-to-digital converters (SAR ADCs) with a synchronous serial interface and low on-resistance switches for driving 4-wire resistive touch screens. The AD7879/AD7889 work with a very low power supply―a single 1.6 V to 3.6 V supply―and feature throughput rates of 105 kSPS. The devices include a shutdown mode that reduces current consumption to less than 6 μA. To reduce the effects of noise from LCDs and other sources, the AD7879/AD7889 contain a preprocessing block. The preprocessing function consists of a median filter and an averaging filter. The combination of these two filters provides a more robust solution, discarding the spurious noise in the signal and keeping only the data of interest. The size of both filters is programmable. Other user-programmable conversion controls include variable acquisition time and first conversion delay; up to 16 averages can be taken per conversion. The AD7879/AD7889 can run in slave mode or standalone (master) mode, using an automatic conversion sequencer and timer. The AD7879/AD7889 have a programmable pin that can operate as an auxiliary input to the ADC, as a battery monitor, or as a GPIO. In addition, a programmable interrupt output can operate in three modes: as a general-purpose interrupt to signal when new data is available (DAV), as an interrupt to indicate when limits are exceeded (INT), or as a pen-down interrupt when the screen is touched (PENIRQ). The AD7879/AD7889 offer temp- erature measurement and touch-pressure measurement. The AD7879 is available in a 12-ball, 1.6 mm × 2 mm WLCSP and in a 16-lead, 4 mm × 4 mm LFCSP. The AD7889 is available in a backside-coated version of the WLCSP. Both parts support an SPI interface (AD7879/AD7889) or an I2C® interface (AD7879-1/AD7889-1). AD7879主要特点: 4-wire touch screen interface 1.6 V to 3.6 V operation Median and averaging filter to reduce noise Automatic conversion sequencer and timer User-programmable conversion parameters Auxiliary analog input/battery monitor (0.5V to 5V) 1 optional GPIO Interrupt outputs (INT, PENIRQ) Touch-pressure measurement Wake-up on touch function Shutdown mode: 6 μA maximum 12-ball, 1.6 mm × 2 mm WLCSP 16-lead, 4 mm × 4 mm LFCSP AD7879应用: Personal digital assistants Smart handheld devices Touch screen monitors Point-of-sale terminals Medical devices Cell phones 图3{京电港论坛}.AD7879典范应用电路原理图纸 AD7879评估板 The AD7879/AD7879-1 evaluation board allows you to evaluate all features of the AD7879/AD7879-1. The evaluation software allows you to change the settings on the AD7879/AD7879-1. You can connect the touch screen to Connector J3 or use the on-board variable resistors to evaluate the touch screen function. AD7879评估板主要特点: Easy access to the AD7879/AD7879-1 Connects to any PC USB port Self-contained evaluation system Test points for easy access to signals Touch screen included 图4{京电港论坛}.AD7879评估板方框架图 详情请复制打开此衔接地址: |
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