Tag Archives: self-capacitance

Your touchscreen can now seamlessly transition between hover, finger and glove touch

The new maXTouch mXT641T family is the industry’s first auto-qualified self- and mutual-capacitance controller meeting the AEC-Q100 standards for high reliability in harsh environments.

Optimized for capacitive touchpads and touchscreens from five to 10 inches, Atmel has expanded its robust portfolio of automotive-qualified maXTouch controllers with the all-new mXT641T family. These devices are the industry’s first auto-qualified self- and mutual-capacitance controllers meeting the AEC-Q100 standards for high reliability in harsh environments.


The maXTouch mXT641T family incorporates Atmel’s Adaptive Sensing technology to enable dynamic touch classification, a feature that automatically and intelligently switches between self- and mutual-capacitance sensing to provide users a seamless transition between a finger touch, hover or glove touch. As a result, this eliminates the need for users to manually enable ‘glove mode’ in the operating system to differentiate between hover and glove modes. Adaptive Sensing is also resistant to water and moisture and ensures superior touch performance even in these harsh conditions.

The latest family of devices support stringent automotive requirements including hover and glove support in moist and cold environments, thick lens for better impact resistance, and single-layer shieldless sensor designs in automotive center consoles, navigation systems, radio interfaces and rear-seat entertainment systems. The single-layer shieldless sensor design eliminates additional screen layers, delivering better light transparency resulting in lower power consumption along with an overall lower system cost for the manufacturer.


“More consumers are demanding high-performance touchscreens in their vehicles with capacitive touch technology,” said Rob Valiton, Senior Vice President and General Manager, Automotive, Memory and Secure Products Business Units. “Atmel is continuing to drive more innovative, next-generation touch technologies to the automotive market and our new family of automotive-qualified maXTouch T controllers is further testament to our leadership in this space. Atmel is the only automotive-qualified touch supplier with over two decades of experience in designing, developing, and manufacturing semiconductor solutions that meet the stringent quality and reliability standards for our automotive customers.”

Interested? Production quantities of the mXT641T are now available. Meanwhile, you can learn all about the entire maXTouch lineup here.

Does your smartphone’s touchscreen support moisture touch?

Recently, I met an Atmel maXTouch customer whose smartphone brand is well recognized by consumers in West and East Africa, competing against smartphones made by global brands like Samsung and Nokia. When the customer selected our touchscreen controller for their smartphone product, they needed two features that were very important for African consumers: robust moisture performance and strong noise immunity. This is hardly a surprise as many African countries have unreliable power supplies, and surge protection is important for electronic devices; additionally, the warm climates in most African countries make robust moisture performance a basic requirement for touchscreen controllers to handle sweaty fingers, palms and faces. When the touchscreen controller has trouble in combating charger noise or moisture presence on the touchscreen, a symptom called “ghost touch” would occur – in other words, when the touchscreen automatically triggers a false touch without the presence of a finger contact at that specific location.


With Adaptive Sensing technology, Atmel’s maXTouch T-series scans the touchscreen of a smartphone using both mutual-capacitance and self-capacitance sensing.


Mutual-capacitance enables true multi-finger touch operations, such as multi-finger gestures and rotations used in gaming apps. However, self-capacitance sensing is much less sensitive to the presence of moisture or water droplets than mutual-capacitance. Atmel’s Adaptive Sensing technology combines the analog signals of both self-capacitance and mutual-capacitance, allowing the embedded maXTouch microcontroller to intelligently determine moisture presence through obvious differences in both measurement deltas for corresponding touch locations. As seen in the example below, here a maXTouch device combines both set of signals to eliminate false touch (a.k.a. ghost touch) typically associated with the presence of moisture on a touchscreen.

Self Cap Measurement - TouchI should point out that a smartphone with an excellent water-resistant rating does NOT necessarily mean that it has a robust moisture performance for its touchscreen. Here is a tidbit of consumer feedback on a premium smartphone with IP58 rating:


In comparison, the OEM customer designs smartphones for African consumers that can offer excellent touch performance with the presence of moisture, thanks to our maXTouch T-series. The maXTouch mXT640T series of touchscreen controllers dynamically switches into a Self-Capacitance based single-touch mode when touches are detected in the presence of significant water. This meaning, the normal touch functionality of a mXT640T touchscreen will be maintained for as long as possible before eventually switching to a single touch operation to maintain reliable operation and prevent false touch conditions. The picture below illustrates how we set the bar for superior water/moisture performance in the market:


All in all, a touchscreen powered by Atmel’s maXTouch T-series controllers can support true multi-finger operations with the presence of moisture. Even in a rainy condition where water falls down to your smartphone, the system dynamically maintains reliable touch operations and prevents false touches, so that when you press a speed-dial for Uber in the rain, your phone will not innocently call your ex-girlfriend instead.


Integrating Capacitive Touchscreens Into Automotive Dashboards

By Stephan Thaler and Thomas Wenzel

As automotive design engineers integrate more sophisticated touchscreen technologies into their vehicles, they are transforming the driver experience. Resistive touchscreens were once the predominant choice because they are easy to control and relatively inexpensive to manufacture. However, they also support lower light transmission and their surfaces are sensitive to scratching. Capacitive touchscreen technology overcomes many of the problems associated with resistive touchscreens, while bringing the familiar advantages of smartphones and tablets.

When a finger approaches the surface of a capacitive touchscreen, this leads to a slight change in capacities of one or more of the underlying sensors. Self-capacitance and mutual capacitance are two ways to map capacity. The self-capacitance method measures the input signal of a complete row and column of electrodes; however, this method doesn’t always unambiguously classify the position when operated with more than one finger. Mutual capacitance measures every point of intersection in the orthogonal mix. Given this, you can exclude gaps in the finger classification that would be visible on the screen. 

When a finger approaches the surface of a capacitive touchscreen, this creates a slight change in the capacities of one or more of the sensors in the screen.

When a finger approaches the surface of a capacitive touchscreen, this creates a slight change in the capacities of one or more of the sensors in the screen.

Unlike resistive technology, with capacitive technology the user’s finger doesn’t need to exert any pressure on the screen surface in order to be recognized. The precise position of the fingers on the touchscreen is calculated when the measured values of all points of the intersection are evaluated. Sensitive touchscreen controllers, such as Atmel maXTouch devices, can even register the approach of one or more gloved fingers.

Since capacity changes in these applications is very small, it’s critical to minimize the impact of noise and interference. Algorithms in the touchscreen controller can address these issues. For example, maXTouch controllers offer interference suppression that allow you to significantly reduce the number of sensor layers above the LCD screen. Post-processing functions also are integral to reliable operation, especially in different environmental conditions.

To learn more about automotive touch displays, read our full article, Capacitive Touch Technology Opens the Door to a New Generation of Automotive User Interfaces.