Atmel mXT768E block diagram
Atmel's popular maxTouch line has received a boost with the latest maxTouch E Family. Leading the pack is the mXT768E (Fig. 1). It supports up to 768 channels and is designed for displays up to 12-in.
The maxTouch E Series is designed to deliver unlimited touch capability while putting the intelligence in the chipset. The multitouch support is configured to handle up to 16 simultaneous touches. This offloads the host processor that is typically running an operating system like Android. The chips have an internal 11-bit precision designed to deliver an 80:1 SNR in mobile applictions. They have a 150Hz response rate.
The new chips employ a split touch engine and microprocessor core. The Atmel AVR32 was tapped for the high end chipset. The other chips in the series that utilize the AVR32 core are the mXT540E and mXT384W. They are designed for smaller displays.
This chips address capacitive touch noise avoidance by automatically changing scanning frequency. Noise suppression is used with the best frequency. The chips can detect a stylus with a tip as small as 2mm. The on-chip processing also can also ignore palms and hand holding issues common with tablets.
The new series also includes the mXT224E, an enhanced version that is pin compatible with an earlier maxTouch chip. It supports 224 channels/nodes and targets displays up to 7-in. The compute engine is an 8-bit XMega core but still delivers a 250Hz update rate. It also support narrow stylus tracking and grip suppression.