Electronic Design
Direct Lamination Multitouch Technology Delivers Top Notch SNR

Direct Lamination Multitouch Technology Delivers Top Notch SNR

Cypress Semiconductor continues to push the envelope when it comes to touch interfaces and its latest TrueTouch Gen 4 looks to leap past the competition. Cypress had already delivered a single layer touch system (see Single Layer Cap Touch Targets Low Cost Resistive Competition) and the latest family of multitouch controller chips builds on this approach. They are built around a 32-bit ARM Cortex core. This provides the ability to implement more sophisticated gesture algorithms. It uses self and mutual capacitance and allows the chips to deliver 0.2 mm accuracy and linearity as well as 1-mm stylus support. It even handles hover mode detection in addition to direct contact.

Cypress Semiconductor's Display Armor technology is designed to eliminate display noise. It does so using two techniques. The first is to listen for noise in the analog front end, and literally subtract it from the measurements. This gives 1Vpp directly coupled noise immunity. For noise above these levels it has a second method whereby the hardware can listen for the horizontal and vertical synch signals, and lock onto them to make measurements effectively in the quiet times. As this is built-in hardware, this approach allows the chips to run at a 400 Hz refresh rate and 1 kHz panel scan rate.

Combine the Display Armor technology with a 10 V Tx built-in drive and designers can eliminate air gaps and shield layers. This means direct lamination and on-cell or in-cell applications (Fig. 1) can be used significantly reducing touchscreen display costs. It also makes the overall system thinner even with low cost, ACVCOM LCDs. Multitouch displays can now be significantly less expensive while being significantly more accurate.

The latest chips also incorporate Charger Armor technology eliminates battery charger related noise. It provides 95Vpp noise immunity. The current crop of chips handles CapSense buttons as well as displays up to 5-in. They can even meet IP-67 waterproofing functionality. Active power consumption is only 2 mW. The deep sleep mode uses 1.8 uW and the system can wake-up via an address match on the COM port.

Cypress Semiconductor TrueTouch Host emulator (Fig. 2) allows designs to configure and tune a system in minutes. It uses the I2C/SPI serial interface to configure the chip. It provides assisted tuning and allows individual features to be enabled or disabled.

Chip scale packaging (CSP) allows the True Touch Gen 4 chips to fit into a 3.8mm by 3.8mm package. Built-in manufacturing test support works with the Cypress Manufacturing Test Kit (MTK). It supports low cost sensor patterns.

TAGS: Components
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