Accelerate EMI qualification with capacitive touch controllers

The TD family of touch controllers features a new differential mutual signal acquisition method that significantly increases the Signal-to-Noise Ratio (SNR). This allows the use of very thick glass or plastic cover lenses and multi-finger thick gloved touch support up to the equivalent of 4.5 mm polymethyl methacrylate (PMMA).

The MXT1067TD, MXT1189TD and MXT1665TD devices add several variants that are cost-optimised for nine- to 13” automotive touchscreens to Microchip’s portfolio and are complemented by the recently introduced MXT449TD, MXT641TD, MXT2113TD and MXT2912TD devices supporting up to 20” touchscreens.

Each device addresses aspects of the increasing demand for functional safety features and is designed in accordance with the Automotive SPICE Level 3 capability and ISO 26262 Automotive Safety Integrity Level (ASIL) B requirements.

All devices in the TD family feature a unique waveform shaping capability to optimise the performance of the touch controller’s radiated emissions through an EMI optimisation tool. Working with product experts in Microchip’s worldwide application design centres, this tool allows developers to enter user-defined RF limits and tune the shape of the transmitted burst waveform used for the touch-sensing acquisition.

Waveform shaping is achieved through firmware parameters derived from the tool and helps designers to position the fundamental burst frequency to work together with other in-vehicle applications, such as the remote keyless entry system. The resulting parameters are then simply added to the maXTouch configuration file, which customises the touch controller performance to the individual customer design.

This process can save the designer many hours, or even weeks, of expensive EMC test chamber time by eliminating experimentation with different configuration settings to achieve the desired EMI/EMC performance.

Microchip provides the most comprehensive automotive touchscreen controller portfolio in the market. Target applications are centre stack displays and navigation systems but are also suitable for industrial applications such as automation and manufacturing stations.

An evaluation kit is available for each of the parts in the new maXTouch touchscreen controller family.

Kit numbers are ATEVK-MXT1067TDAT-A (I2C), ATEVK-MXT1189TDAT-A (I2C), ATEVK-MXT1189TDAT-C (SPI), ATEVK-MXT1665TDAT-A (I2C) and ATEVK-MXT1665TDAT-C (SPI). Each kit includes a Printed Circuit Board (PCB) with the maXTouch touchscreen controller, a touch sensor on a clear glass lens, the Flat Printed Circuit (FPC) to connect to the sensor, and a bridge PCB to connect the kit to the host computer via USB, as well as cables, software and documentation.

All parts are also compatible with maXTouch Studio, a full software development environment to support the evaluation of maXTouch touchscreen controllers.

The maXTouch EMI optimisation service will be made available as part of the system support provided by one of Microchip’s worldwide application design centres.

The MXT1067TD, MXT1189TD and MXT1665TD devices are available now in sampling and volume quantities in TQFP128 (MXT1067TD only) and LQFP144 packages.