Tag Archives: EW

Electronics Weekly talks Atmel touch chips

Earlier this week, Atmel expanded its popular maXTouch T lineup of touchscreen controllers with the mXT640T, mXT336T and mXT224T. The new devices offer a comprehensive set of features, supporting next-gen mobile devices such as smartphones, phablets and mid-size tablets with touchscreens ranging from 3.2”-8.3.”

In covering the launch, Steve Bush of Electronics Weekly (EW) noted that there are now 20 DACs taking data off 20 sense wires followed by parallel processing, compared with 18 wires multiplexed onto fewer ADCs before. In addition, having moved to a 130nm process for the new chips, there was also room for Atmel to replace the 8-bit processor with a 32-bit AVR core.

“It is a lot more power efficient and has a lot more processing capability for a lot more intelligence: large finger detection, palm rejection, water rejection and charger noise immunity,” Atmel product marketing manager Tony Xia told Electronics Weekly. “And it can work with xSense, our scheme to use fine copper wires to replace ITO.”

As well as replacing increasingly hard to get ITO (indium tim oxide), xSense reduces sense line impedance, allowing the wire to be charged and read faster. Simply put, with more sense cycles in a fixed time, statistical processing can reduce the effective signal-to-noise ratio.

“Charger noise rejection is actually a combination of better numerical processing, actively hopping the read frequency away from the charger band, and analogue processing,” Xia explained.

In terms of interacting with water and gloves, Xia confirmed there “is no impairment” for condensation with a finger.

“[Similarly, with] wet hands from washing, there is no problem; up to a few drops, there is no false touch,” he stated. “[Plus], a lot of smartphones today won’t work with gloves at all. [In contrast], ours worked well with 20 different gloves we were presented with on one customer visit.”

Lastly, said Xia, passive styluses no longer need to be conductive and in electrical contact with the user.

“We tried it with a cheap mechanical pencil with an 0.5mm lead and it worked,” he added.