Touch-Sensor IC Targets On/Off/Wake-Up Control
The STM8T141 touch-sensor controller from STMicroelectronics is designed to improve the performance and styling of products such as mobile phones, portable consumer products, and appliances. Already in production for a leading cell-phone maker, the eight-pin STM8T141 draws a current as low as 11 µA from the battery.
The chip also can detect user presence via the touch-sensor electrode, responding quickly to wake the system from a low-power sleep mode. It’s designed to monitor a single touch-sensing electrode embedded on the control panel of the end product or in the outer casing. The sensor may be hidden, or its position indicated using a printed, overlaid, or illuminated icon.
The controller supports proximity sensing, allowing equipment to be controlled without direct user contact. This allows the sensor to control power-saving features such as system wake-up on user detection, or features for added convenience such as automatic backlight activation supporting find-in-the-dark capability. Hence, using the STM8T141 for touch or proximity detection helps product stylists achieve their desired look and feel in various product designs.
The STM8T141’s built-in calibration and compensation save time during product manufacture. The chip also enables touch sensing to operate reliably for the lifetime of gadgets such as kitchen appliances, universal remote controls, game terminals, home-A/V products, wireless keyboards, personal media players, audio headsets, and many other products. Further, the device supports a driven electrode-shielding wire, which protects against noise from external sources without the reduction in electrode sensitivity experienced with a grounded shield.
Additionally, the STM8T141 offers a configurable single output for reporting touch or proximity detection and four sensitivity levels allowing adjustment for panel material and thickness. It also boasts low consumption, drawing 11 µA in low-power mode and 30 µA in run mode. It uses a capacitive-charge-transfer sensing technique. Its on-chip voltage regulator enables enhanced performance and low parts count. It features self-calibration and automatic recalibration. And, it provides an environment compensation filter, sensitivity threshold, and de-bounce filter.
The available STM8T141-EVAL evaluation kit provides an easy-to-use, low-cost demonstration of the chip’s touch and proximity features. In addition, the ST-TSLINK programming dongle and STM8T14X-SB socket programming board are used with the STVP PC-based programming tool for fast and efficient product configuration.
The STM8T141 is already sampling in the 3- by 2- by 0.6-mm ultra-small and low-profile DFN8 package. In quantities of 10,000, the controller costs $0.45 each.
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