基于STM8T141設計的觸摸或接近檢測方案

STM8T141是ST 公司的ProxSense單路全集成電荷傳輸的容性傳感器,內置了驅動屏蔽功能,用于觸摸或接近檢測,在成本敏感應用中替代傳統的機械開關.主要用在消費類電子,家庭和辦公設備,電池和關鍵電源應用等.本文介紹STM8T141主要特性,方框圖, 測量電路圖, 典型應用電路圖以及表面電容傳感器等效電容電路, 手提應用等效電路圖和STM8T14X-EVAL 評估板主要特性, 評估板和模塊(MB858)的電路圖.

STM8T141: Single-channel capacitive sensor for touch or proximity detection with shielded sensing electrode

The STM8T141 is a ProxSense? single-channel, fully integrated, charge-transfer,capacitive sensor that is designed to replace conventional electromechanical switches in cost-sensitive applications.

The STM8T141 is offered in 8-pin packages and is ideally suited for 1-button applications. It can be configured either in touch or proximity sensing mode for wake-up or backlighting on actuation. The extremely low current consumption makes it an ideal solution for battery-powered applications.

The device features an internal voltage regulator to enhance detection sensitivity and stability. The STM8T141 touchpad can sense through almost any dielectric and can thereby contain the electronics in a sealed environment.

The STM8T141 also incorporates the advantages of using a driven shielding capability. This makes it possible to separate the sealed electronics from the sensing electrode. The shield feature enables the designer to protect part of the sensing element from unwanted environmental interference and enhances proximity detection when used with battery (DC) applications.

STM8T141主要特性:

■ Touch or proximity detection (a few centimeters)

■ Built-in driven shield function:

– Enhance proximity detection

– Protect sensing electrode from noise interference

■ Ultra-low power modes suitable for battery applications (11 μA in extreme low power mode)

■ On-chip integrated voltage regulator

■ Environment compensation filter

■ User programmable options include:

– Four detection thresholds

– Four output modes

– Four low power modes

– Reference freeze timeout

■ Minimal external components

STM8T141應用:

■ Consumer electronics

■ Power-critical and battery applications

– Wake-up on proximity

■ Home and office appliances

– Find-in-the-dark (FITD) applications using proximity detection

– Sanitary ware and white goods

■ Flameproof human interface devices for use in hazardous environments

圖1.STM8T141方框圖

圖2.STM8T141測量電路圖

圖3.STM8T141典型應用電路圖

圖4.表面電容傳感器等效電容電路

圖5.手提應用等效電路圖

STM8T14X-EVAL 評估板

The STM8T14X-EVAL is an evaluation kit which introduces developers to STMicroelectronics STM8T141 touch and proximity capacitive sensor. It contains an STM8T141 evaluation board, the MB858, plus a set of preconfigured plug-in modules which allow to evaluate STM8T141 device performances in either touch or proximity detection (depending on the module which has been plugged in).

STM8T14X-EVAL 評估板主要特性:

The evaluation kit features are the following:

■ Touch detection with on-board PCB sensing electrode and 1.5 mm dielectric panel

■ Easy dielectric adjustment by stacking acrylic panels

■ Proximity detection with on-board PCB sensing electrode or plug-in antenna

■ Standalone power configuration using an on-board battery

■ External power supply through USB interface

■ Electrode grounding or shielding configured by jumper

The STM8T14X-EVAL kit includes:

● 1 STM8T141 evaluation board (MB858)

● 4 STM8T141 preconfigured plug-in modules (MB856)

● 1 antenna shielding cable

● 1 additional 3 mm acrylic panel


圖6.STM8T14X-EVAL 評估板外形圖

圖7. MB858評估板和插入STM8T141模塊

圖8. STM8T141評估板(MB858)電路圖

圖9. STM8T141模塊(MB858)電路圖