Capacitive touchscreen controllers for home/factory use

October 12, 2021 // By Jean-Pierre Joosting
Capacitive touchscreen controllers for home/factory use
Functional-safety-certified family of capacitive maXTouch® touchscreen controllers extended to address screen sizes beyond 10 inches.

Networked and connected home appliances enable both users and manufacturers to communicate with them via the internet. For example, the user of a kitchen oven might look up a new recipe online or a manufacturer might perform remote diagnostics or over-the-air firmware updates. Displays and touch sensors are essential for enabling this functionality in modern appliances. Microchip Technology is adding two new members to its family of IEC/UL 60730 Class B certified touchscreen controllers. The latest MXT448UD-HA and MXT640UD-HA extend the Class B portfolio of devices beyond 10 inches, thus providing dedicated solutions for larger screen sizes as well as scalability to customers.

In addition to Class B, these new devices are also compliant with the IEC61000-4-6 Class A specification for conducted noise immunity up to 10 Vrms (level three for industrial use). This enables products with a touch screen interface to function in very harsh factory environments where electromagnetic interference can be caused by conveyer belts, power rails or assembly machinery. Manufacturers of home appliances will benefit from an increased reliability and production yield. This is a big improvement for consumers using unprotected touchscreens on an oven or washing machine that may result in concern for false or missed touches caused by electromagnetic interference from unshielded power transmission, electric motors, and neighboring electrical equipment.

These new touchscreen controllers also come with two serial interfaces (SPI and I²C) that operate simultaneously allowing redundancy in a design through the integration of safety features, such as individual communication between the touchscreen controller to the host microprocessor (MPU) in addition to a safety microcontroller (MCU). Touch events are provided to both processors at the same time. This unique architecture shortens time to market and reduces development cost by allowing all safety-critical firmware to be developed on a dedicated safety-certified MCU (with mandatory source code review by an IEC/UL test lab) separate from the main processor running the appliance’s Graphical User Interface (GUI).


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