MK715
Touch Screen Controller
General Description
The
MK715
Touch Screen Controller IC provides all the
screen drive, Analog to Digital converter (ADC) and
control circuits to easily interface to 4-wire analog resistive
touch screens. It also includes a general purpose A to D
converter and a clock synthesizer.
The IC continually monitors the screen waiting for a
touch. In this mode, the supply current is typically 4µA.
When the screen is touched, the IC performs analog to
digital conversions to determine the location of the touch,
stores the X and Y locations in the registers, and issues
an interrupt. This process is repeated up to 303 times per
second until no further screen touches are detected, at
which time the low current mode is resumed.
The device has a general purpose input into the 10-bit
ADC, allowing for the measurement of other inputs such
as battery voltage. The MK715 can be powered from a
3.3V supply, and uses an inexpensive 32.768kHz watch
crystal as the input reference. An internal Phase-Lock
Loop clock synthesizer provides the high speed clock for
the ADC, and the option to have a clock output to drive
other digital chips in the system.
The tiny package is the same body size as the 14 pin
SOIC, with 25 mil spacings on the leads.
Features
Tiny 20 pin SSOP (150 mil body)
4 microamp standby current
Less than 3mA active current at 3.3V, including
screen drive
Touch pressure can be measured
One or two general purpose A to D inputs
On-chip voltage reference
32.768kHz crystal/clock input
MHz clock outputs available
Operates with four wire touch screens
Ratiometric conversion eliminates screen
calibration
Automatic wake up upon screen touch
Programmable conversion rate to a maximum of
303 points per second
3.3V or 5V supply (2.7V version available)
10 bit A/D converter
Full powerdown control
Touch screen is directly driven - no external
transistors are required
A to D Converter guaranteed monotonic
3 or 4 wire serial interface
Applications
Notebook Computers
Handheld Computers
PDAs
Touch-screen kiosks
Pin Assignment
SK
D0
DI
TOUCH#
XH
XL
YH
YL
PL
GP
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
CS
CLKOUT
INT
VDD
X2
X1
GND
CAP2
CAP1
CAP3
MK715
20 pin SSOP
MK715RevD020200
ICS reserves the right to make changes in the device data identified in this publication
without further notice. ICS advises its customers to obtain the latest version of all device
data to verify that any information being relied upon by the customer is current and accurate.
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