基于SX8652设计的4线和5线电阻触摸屏控制技术

SX8652是Semtech公司的非常低功耗高度可靠的 4线和5线电阻触摸屏控制器,输入电压从1.65V到3.7V,具有工作在74KSPS的精密高速12位SAR ADC,吞吐量为5000(X-Y)座标/秒.关断模式小于1uA,SPI串行接口.主要应用在手机,数码相机,激光打印机和MP3播放器.本文介绍了SX8652主要特性, 简化方框图以及4线和5线触摸屏应用框图与SX8652 评估板电路图.

The SX8652 is a very low power, high reliability controller for 4-wire and 5-wire resistive touch screens used in PDAs, portable instruments and point-of-sales terminal applications. It features a wide input supply range from 1.65V to 3.7V and low power modes to preserve current when the screen is unintentionally touched.

To compute touch screen X-Y coordinates and touch pressure with precision, a low power 12-bit analog-digital converter is activated with the possibility to enable on-chip data averaging processing algorithms to reduce host activity and suppress system noise.

The touch screen controller inputs have been specially designed to provide robust on-chip ESD protection of up to ±15kV in both HBM and Contact Discharge, and eliminates the need for external protection devices. The SX8652 is controlled by a high speed SPI™ serial interface.

The SX8652 is available in a 4.0 mm x 3.0 mm 14-DFN package and a 1.5 mm x 2.0 mm wafer level chip scale package (WLCSP) for space conscience applications.

Extremely Low Power Consumption: 23uA@1.8V 8kSPS

Superior On-chip ESD Protection

_±15kV HBM (X+,X-,Y+,Y-)

_±2kV CDM

_±25kV Air Gap Discharge

_±15kV Contact Discharge

_±300V MM

SX86524主要特性:

Single 1.65V to 3.7V Supply/Reference

4-Wire or 5-Wire Resistive Touch Screen Interface

Integrated Preprocessing Block to Reduce Host Loading and Bus Activity

Four User Programmable Operation Modes provides

Flexibility to address Different Application Needs

_Manual, Automatic, Pen Detect, Pen Trigger

Low Noise Ratiometric Conversion

Precision, High Speed 12-bit SAR ADC Operating At 74k SPS

Throughput: 5000 (X-Y) coordinates/second (c/s) with 7-Sample Averaging

Low Power Shut-Down Mode < 1uA

SPI™ Serial Interface

Touch Pressure Measurement (4-Wire)

Auxiliary Input (4-Wire) For Alternate ADC Input or Start of Conversion Trigger

Hardware & Software reset

-40℃ to +85℃ operation

Pb-Free, Halogen Free, RoHS/WEEE compliant product

Windows CE 6.0, Linux Driver Support Available

Packages: 14-LD (4.0 mm x 3.0 mm) DFN 12-Ball (1.5 mm x 2.0 mm) WLCSP

SX86524应用:

Cell Phone

Digital Still Camera

Laser Printer

MP3 Player


图1.SX8652简化方框图

图2.SX8652应用框图

图3.SX8652 4线触摸屏应用框图

图4.SX8652 5线触摸屏应用框图

SX8652 评估板

The SX8652EVK is the board for evaluation of the 4/5 wire resistive touch screen controller SX8652. It is provided with a 4-wire touch screen to ease the evaluation.

No external supply is needed to power the board. A USB cable is provided to connect the EVK to a Windows based PC for operation of the software.

The evaluation kit is composed of the following parts:

i) The board with the SX8652 and the touch screen on the top

ii) A USB cable to connect the board to the PC

iii) A CDROM with the installation files and the user guide

iv) A stylus to write on the touch screen

This evaluation board contains the following main components that can be identified from the schematics in section

SX8652 in DFN package

FT2232D with the quartz : USB to SPI controller

M93C46 EEPROM : USB initialization information

SN74LVC8T245 : Level shifter

SC1563:Regulator for 3.3V and 1.85V

4-wire touchscreen connected in J5


图5.SX8652 评估板电路图