Touch-screen controller provides tactile feedback
By Paul Rako, Technical Editor -- EDN, August 6, 2009
Maxim Integrated Products recently announced the MAX11810 touchscreen-interface chip. The device generates the output voltage to excite a four-wire resistive touchscreen and includes ADCs to read back a touch position. It also provides haptic feedback by rotating a vibrator motor or pulsing a piezoelectric transducer on the LCD screen. It excites and reads back an IR (infrared) photodiode to sense when the screen is pressed against your face. This feature allows it to ignore the inputs and suppress the haptic outputs. A sister part, the MAX11811, has identical functions but employs a 400-kHz I2C (inter-integrated-circuit) interface instead of a 25-MHz SPI (serial-peripheral interface). Both parts operate from a 1.7 to 3.6V power supply and feature 12-bit ADCs. At a 34.4k-sample/sec rate, the device consumes 246 mW at 1.8V or 698 mW at 3.6V.
Applications include cell phones, MP3 players, portable media players, digital photo frames, multifunction printers, point-of-sale terminals, bar-code scanners, card readers, and other industrial equipment. Automotive-qualified-part versions exist for use in car GPSs (global-positioning systems), entertainment head units, and rear-seat-entertainment systems. The product has a state machine for onboard processing of touch events to validate them before sending the data to the system microprocessor. The onboard processing can also supply an improved capture rate of as many as 161 coordinates/sec.
The MAX11810 operates over a −40 to +85°C temperature range and comes in 2.1×2.1-mm, 20-pin TQFN packages and 16-pin WLPs. It sells for $1.81 (1000) and is available now, along with evaluation kits that include a touchscreen and a dc motor.
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Designed to use in cell phone. So you press against your face while making calls. Think iphone.
Tony Rolando - 2009-28-9 07:19:00 PDT -
Re: "It excites and reads back an IR (infrared) photodiode to sense when the screen is pressed against your face."
Why would I press this against my face?
Larry Hines - 2009-24-8 05:35:00 PDT -
Having read the preliminary datasheet, the power consumption is stated as 246uW @ 1.8V and 698uW @ 3.6V. The figures of mW in the article are incorrect (x1000!).
Mark Sansom - 2009-19-8 00:55:00 PDT
