Touchscreen controller supports multiple screen formats

New Products | November 30, 2021

By Christoph Hammerschmidt

Sensing / Conditioning Analog Automotive Displays & Interfaces

The MXT1296M1T can reconfigure its driving and receiving touch channels to match the specific display format, from 1:1 to 5:1, including the 8:3 aspect ratio popular in automotive applications. This feature allows customers to take advantage of the number of touch channels available without having to rely on larger and more expensive touch controllers. It also saves additional development and validation time and resources by reusing a common PCB design to support different touch sensor aspect ratios. As an industry first, the MXT1296M1T allows reconfiguration of sensor channels via parameters. These settings do not require a firmware change, enabling lower design risk and faster time-to-market.

The maXTouch touchscreen controller offers two communication interfaces working in parallel, providing a seamless connection to the LVDS video link return channel for touch information and a connection to a local microcontroller (MCU). This seamless topology reduces touch latency and thus improves ease of use. In addition, this topology guarantees full compatibility with the maXTouch software drivers, which are available for all major automotive operating systems such as Linux, Android™ and QNX.

When connected to a suitable local MCU, the second interface provides:

A redundancy connection to the main unit via a CAN bus or a 10BASE-T1S automotive Ethernet connection for increased system-level functional safety.
Local access and control over maXTouch touchscreen controller functions, such as a capacitive button report, live touch sensor diagnostics, and raw data for external and custom post-processing
A secured over-the-air firmware update function with Microchip’s TrustAnchor100 companion chip.

The MXT1296M1T includes several functional safety features to permanently verify the integrity of the touch controller operation as well as any of the connected touch sensors. The Failure Modes Effects and Diagnostic Analysis (FMEDA) and Functional Safety Manual provide customers with significant relief when designing, building and certifying a system for Automotive Safety Integrity Level B (ASIL-B) applications to the ISO 26262 standard.

The device enables high-resolution control of the transmit waveform to reduce RF emissions and avoid interference with the car radio or RFID systems. The larger the screens in vehicles become, the more RF emissions are generated by the projected capacitive touch technology. Every major car manufacturer works with different emission limits in terms of amplitude, frequency and bandwidth. To accurately shape the waveform on the transmission lines, the MXT1296M1T uses a dedicated on-chip digital-to-analogue converter (DAC) with 64 levels. This allows designers to precisely control frequency response and optimise harmonic emissions to meet specific OEM limits.

The latest version of the maXTouch Studio integrated development environment (IDE) supports configuration and tuning of the MXT1296M1T.

The MXT1296M1T is now in series production. ISO 26262 FMEDA and FuSa manual will be available from Q1/2022.

www.microchip.com