DATASHEET TOUCH SCREEN CONTROLLER MK712 Description Features The MK712 Touch Screen Controller IC provides all the Packaged in 28-pin SSOP (150 mil) or 28-pin SOIC (300 screen drive, A to D converter and control circuits to easily mil) interface to 4-wire analog resistive touch screens. Industrial (-30C to +70C) and commercial (0 to +70C) and automotive (-35C to +85C) temperature ranges The IC continually monitors the screen waiting for a touch. In this mode, the supply current is typically 0.5A. When Pb (lead) free the screen is touched, the IC performs analog to digital Fully integrated, lowest power solution conversions to determine the location of the touch, stores Low standby current of 0.5A (typical) at 5.0 V the X and Y locations in the registers, and issues an Active current while converting less than 10 mA interrupt. This process is repeated up to 197 times per second until no further screen touches are detected, at Resolves 350 dots/inch on 10.5 display which time the low current mode is resumed. Maximum speed of 197 points/second Ratio metric conversion may eliminate screen calibration Automatically wakes up and goes back to standby Block Diagram 3.3 V or 5 V supply 12 bit A/D converter Simplifies the writing of software for touch screens Extended temperature range available Capacitors are the only external components required Touch screen is directly driven - no external transistors are required Programmable conversion rate A to D Converter is monotonic Parallel interface Pin Assignment NC 1 28 D0 INT 2 27 D1 TOUCH 3 26 D2 VDD 4 25 D3 VDD 5 24 D4 XH 6 23 D5 XL 7 22 VDD YH 8 21 GND YL 9 20 D6 10 19 GND D7 GND 11 18 CLKIN 12 17 WR A0 RD 13 16 A1 CS 14 15 A2 IDT TOUCH SCREEN CONTROLLER 1 MK712 REV N 051310MK712 TOUCH SCREEN CONTROLLER TOUCH SCREEN CONTROL Pin Descriptions Pin Pin Pin Type Pin Description Number Name 1 NC No connect. Do not connect this pin to anything. 2 INT Output Interrupt. Goes high to signal an interrupt. Cleared on next read. 3 TOUCH Output Touch signal. Goes low when screen is touched. Goes high when not touched. 4 VDD Power Power Supply. Connect to +5 V or +3.3 V. (Connect all VDDs to same voltage) 5 VDD Power Power Supply. Connect to +3.3 V. 6 XH Touch Screen Pin Connect to X-high on touch screen. (Right side) 7 XL Touch Screen Pin Connect to X-low on touch screen. (Left side) 8 YH Touch Screen Pin Connect to Y-high on touch screen. (Top) 9 YL Touch Screen Pin Connect to Y-low on touch screen. (Bottom) 10 GND Power Connect to ground. 11 GND Power Connect to ground. 12 WR Input Write enable. Active low. 13 RD Input Read enable. Active low. 14 CS Input Chip select. Active low. 15 A2 Input Register address 2. 16 A1 Input Register address 1. 17 A0 Input Register address 0. 18 CLKIN Input Clock input. Typically 14.3 MHz. Best if driven by an IDT clock synthesizer. 19 D7 I/O Data bit 7. 20 D6 I/O Data bit 6. 21 GND Power Connect to ground. 22 VDD Power Power Supply. Connect to +5 V or +3.3 V. (Connect all VDDs to same voltage) 23 D5 I/O Data bit 5. 24 D4 I/O Data bit 4. 25 D3 I/O Data bit 3. 26 D2 I/O Data bit 2. 27 D1 I/O Data bit 1. 28 D0 I/O Data bit 0. Interrupts Interrupts are controlled by register 6 (see Register Description). The INT pin (pin 2) goes high to signal an interrupt. Interrupts are then cleared by reading any register. However, if the MK712 is in the process of generating an interrupt during a read cycle, then the interrupt is not cleared and INT will stay high. This internal process may take 100ns, and so to guarantee that the interrupt is cleared, two successive read cycles may be necessary. IDT TOUCH SCREEN CONTROLLER 2 MK712 REV N 051310