原标题：Atmel mXT224 224节点触摸屏传感方案

　　Atmel 公司的mXT224 是224节点高度可配置触摸屏控制器,是maXTouch产品平台中一员.该器件把专利的电荷传输器和XMEGA技术组合起来,具有真正12位的多次触摸性能,宽达4.3吋对角线屏,有224路通路,支持电极可配置的20(X)x(Y)网格线和maXTouch触目惊心键.主要用在手机,手机游戏机,个人导航仪和笔记本电脑等.本文介绍了mXT224的主要特性,应用领域和应用电路.

　　maXTouch™ 224-channel Touchscreen Sensor IC

　　The mXT224 is a 224-node highly configurable touchscreen controller which is part of Atmels maXTouch™ product platform. By combining Atmels patented Charge Transfer and XMEGA™ technologies, Atmels engineering teams have produced an optimal and scalable architecture which enables smart processing of a capacitive touch image to accurately regenerate and report the users interaction with the touchscreen.

　　The device features multi-touch performance, enabling touches to be identified and individually tracked and allowing a range of built-in gestures to be reported to the host processor. A wealth of information is provided from the IC, with position data of 12-bit x 12-bit resolution as well as information on the size and angle of touch. The device is extremely responsive - position data is reported at >250Hz making it suitable for use with demanding applications such as handwriting recognition. Due to the high Signal-to-noise ratio (SNR) of up to 80:1 the device works well with fingertip touch and can also be used with a conductive stylus. It has been designed to work in demanding, rapidly changing environments, and with only the touchscreen area being touch-sensitive allows design freedom to place the chip on the main board or adjacent to the sensor.

　　The mXT224 is ideally suited to mobile phone sized touchscreens. It can also be used effectively on screens of up to 10.2", supporting single-touch or two-touch with a larger finger separation.

　　mXT224主要特性:

　　• maXTouch™ Touchscreen

　　– True 12-bit multi-touch with independent XY tracking for up to 10 concurrent touches in real time with touch size reporting

　　– Up to 4.3 inch diagonal screen size supported with 10 mm “pinch” separation

　　– Up to 10.1 inch support with correspondingly wider “pinch”

　　• Number of Channels

　　– Up to 224 (subject to other configuration limitations)

　　– Electrode grid configurations up to 20 X by 10 Y lines supported (subject to 30 total pins and a maximum of 14 Y lines)

　　• maXTouch Touch Key Support

　　– Up to 32 channels can be allocated as fixed keys (subject to other configurations)

　　• Zero Additional Part Count

　　– 16 X by 14 Y matrix (224 channels) implementable with power bypass capacitors only

　　• Signal Processing

　　Advanced digital filtering using both hardware engine and firmware

　　Self-calibration

　　– Auto drift compensation

　　– Adjacent Key Suppression® (AKS™) technology

　　– Grip and face suppression

　　– Reports one-touch and two-touch gestures

　　– Down-scaling and clipping support to match LCD resolution

　　– Ultra-fast start-up and calibration for best user experience

　　– Supports axis flipping and axis switch-over for portrait and landscape modes

　　• Scan Speed

　　– Maximum single touch >250Hz, subject to configuration

　　– Configurable to allow power/speed optimization

　　– Programmable timeout for automatic transition from active to idle states

　　• Response Times

　　– Initial latency <10 ms for first touch from idle, subject to configuration

　　• Sensors

　　– Works with PET or glass sensors

　　– Works with all proprietary sensor patterns recommended by Atmel®

　　– Works with passive stylus

　　• Panel Thickness

　　– Glass up to 3 mm, screen size dependent

　　– Plastic up to 1.5 mm, screen size dependent

　　• Interface

　　– I2C-compatible slave mode 400 kHz

　　• Dual-rail Power

　　– Interface 1.8V to 3.3V nominal, analog 2.7V to 3.3V nominal

　　• Power Consumption

　　– Idle 80Hz: <1.8 mW, subject to configuration

　　– One Touch Active 80Hz: 3.9 mW, subject to configuration

　　– Sleep: 4.5 μW

　　• Package

　　– 49-ball UFBGA 5 x 5 x 0.6 mm, 0.65 ball pitch

　　–49-ball VFBGA 5 x 5 x 1 mm, 0.65 ball pitch

　　图1.mXT224典型应用

　　图2. mXT224典型应用电路