Electronic Design

Single Layer Multitouch Cuts Cost In Half

Multitouch is a requirement for smartphones and tablets and reducing the cost of this feature can have a significant impact on the overall price of a product. Cypress Semiconductor's TrueTouch line goes single layer (see Groundbreaking Multitouch Technology Puts Innovation At Your Fingertips). Its latest SLIM (single layer independent multitouch) architecture (Fig. 1) improves on the initial single layer approach that supported two touches. SLIM brings the technology on par with the more expensive dual layer approaches.

 

Fig. 1: The SLIM (single layer independent multitouch) architecture minimizes cost while improving multitouch performance.

 

SLIM uses a single ITO layer and it does not require any bridges. Cypress Semiconductor is not talking about the actual layout of the layer but is likely to be similar to the triangular layout of earlier single layer technology (Fig. 2). This has connections on two sides but the electrodes do not cross over each other like 2D or 1.5D technologies.

SLIM handles displays up to 4.5-in (diagonal). It can also work with borderless displays up to 3.5-in. This is key to smartphones that are almost all display allowing more interface and display area while reducing the overall size of the phone. The approach can cut the cost of multitouch in half. Does not require a glass layer and it can be put on the PET layer. It can also be placed directly on the display without a PET layer.

 

Fig. 2: SLIM has sensors connections on either side of the display.

 

Cypress Semiconductor's TMA140 family is designed to work with SLIM. It will handle screens up to 4.5-in. It utilizes frequency hopping to reduce noise and it has an accuracy of 0.48 mm and a linearity of 0.4 mm.

Better accuracy and noise immunity are key to SLIM support. The XY layout of most multilayer approaches allows easier interface electronics design while a single layer requires higher accuracy for the sensor interface.

The technology should scale to large displays normally used in tablets. That should have a significant impact on the market effectively eliminating resistive touch display for most consumer applications.

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