PORTLAND, Ore.—Touchscreens for mobile handsets, personal navigation devices, handheld gaming platforms and other pocket-sized electronic devices can be built more inexpensively by adopting a the world's first single-layer multi-touch capacitive controller, according to Integrated Device Technology Inc. (IDT).
Called PureTouch, IDT claims its new technology not only reduces the price of touchscreens, but also lowers their power consumption and increases the effective brightness of both liquid-crystal dispalys (LCDs) and active-matrix light-emitting-diode screens (AMOLED).
"We are announcing the world's first single-layer multi-touch capacitive touchscreen solution," said Alvin Wong, general manager at IDT. "Typically there are two- or three-layers of ITO [indium tin oxide] used for multi-touch screens, but we are borrowing intellectual property from our capacitive button ICs to bringing down the cost of touchscreens, to lower their power consumption, and to increase backlight transmittance, by using just a single layer or ITO."
Because IDT requires only a single layer of transparent conductors to connect transparent on-screen sensor pads, it is also compatible with alternatives to ITO, which is in increasingly sort supply. IDT's new PureTouch technology works fine with ITO, but the company is hedging its bets by working with touchscreen manufacturers who are experimenting with ITO substitutes. The least expensive of these enable the fabrication of touchscreens at low-temperatures and normal atmospheric pressures using roll-to-roll presses for cheap mass production of inexpensive flexible touchscreens.
Multi-touch screens today, on the other hand, depend on multiple layers of ITO so that the location of fingers can be ascertained with simple algorithms that merely read out their coordinates. IDT, on the other hand, has adapted the IP from its current line of capacitive button controller chips to perform the same task with smart algorithms and a single layer sensor pads.
"It's easy to locate fingers with two- and three-layer touchscreens, because they use a x- and y-grid," said Wong. "But determining a finger's location or a single-layer touchscreen requires a smarter algorithm and a more uniform pattern for the sensors—in order to provide reliable touch detection with linearity in any direction and no ghosting."
As a result, IDT claims ultra-cheap single-layer touchscreens can now recognize the same multi-touch gestures that the more expensive two- and three-layer screens recognize. IDT's chip also houses a 32-bit microcontroller with its own flash memory, allowing IDT customers to design their own custom gestures for programming into the controller chip. The only limitation, according to IDT, is that the single-layer approach only works well on screens of five inches or smaller, providing 10-bit resolution (1024-by-1024 pixels).
Prototype touchscreen using IDT's proprietary PureTouch single-layer multi-touch capacitive technology.
The new IDT PureTouch technology can handle up to 35 sensor touchpads, some of which can be used for dedicated buttons. For the touchscreen, IDT's smart algorithm interpolates the location of fingers between pads by virtue of the geometry of its proprietary layout pattern, which, for now, IDT is keeping to itself.
"We know that the first products using our single-layer multi-touch controllers will be torn down revealing our proprietary layout pattern for the sensor pads, but we don't want to give our competitors a head-start now," said Wong.
IDT will begin delivery of its new multi-touch capacitive touchscreen controller chips later this year, with most end-user products using them arriving in 2012 with a few potentially being introduced before the Christmas season this year.
The IDT LDS7000 controls up to 30 touchpads from a five-by-five millimeter, 40-pin TQFN package, while the 35-pad LDS7001 uses a six-by-six millimeter, 48-pin TQFN package.