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UR7HCTS2-S840-FG Schematic ( PDF Datasheet ) - Semtech Corporation

Teilenummer UR7HCTS2-S840-FG
Beschreibung High-Performance/ Low Power Touch Screen Controller/Digitizer
Hersteller Semtech Corporation
Logo Semtech Corporation Logo 




Gesamt 16 Seiten
UR7HCTS2-S840-FG Datasheet, Funktion
ScreenCoderTM UR7HCTS2-S840
High-Performance, Low Power
Touch Screen Controller/Digitizer
HID & SYSTEM MANAGEMENT PRODUCTS, MOUSECODERTM FAMILY
DESCRIPTION
The ScreenCoderTM SPI/Serial is a
touch screen controller and
integrated digitizer IC designed
specifically for RISC-based
systems, such as wireless Internet
appliances. The small, single
footprint IC interfaces the system
via either the Serial Peripheral
Interface (SPI) or Asynchronous
Serial Interface.
Unlike simple A/D implementations,
the ScreenCoderTM SPI/Serial does
not require complicated software
drivers and no processing burden
is placed on the CPU. Due to the
IC’s superior data processing and
sampling rate, the ScreenCoderTM
SPI/Serial is ideal for use in systems
requiring handwriting recognition.
Patented-power management
techniques are also implemented
so that the IC only consumes 1uA
of current most of the time, even
with the external mouse connected.
The IC operates at 3 to 5 Volts.
FEATURES
• Touch screen controller / digitizer
in a single, small footprint IC
• Interfaces the system via either
Serial Peripheral Interface (SPI)
and Asynchronous Serial Interface
• Works with any 4- or 8-wire
resistive touch screen, regardless
of size, material or vendor
• Provides high resolution of 1000
points per axis and a sampling
rate of 200Hz
• Accurate, quick touch response
due to advanced sampling
technology and patented
algorithms
APPLICATIONS
• Wireless Internet Appliances
• Handheld PCs (H/PCs)
PIN ASSIGNMENTS
• Zero-PowerTM operation — IC
typically consumes less than 1µA
• Highly resistant to RF and other
noise sources
• Uses sophisticated power
management for maximum power
savings
• Offers external PS/2 port for the
hot-plug connection of an external
PS/2 pointing device
• Capable of providing other
features, such as battery
monitoring and GPIO
• PS/2 and USB interfaces available
• Available in small 7mm X 7mm
32-pin LQFP package
• Web Phones
• Portable Systems
Features of Semtech’s motion
algorithm include resistance to RF
and other noise which provides
smooth and precise motion control.
The UR7HCTS2-S840 also works
flawlessly with any 4 or 8-wire touch
screen, regardless of size or
manufacturer.
The cost-effective solution requires
few external components, allowing
for a simple and real estate saving
implementation.
24
25
_RB
RSVD2
TxD
ISEL/SCLK
SOUT
_PWR_DOWN
SXL
SYT
32
1
LQFP
17
16
_RTS/_SS
XL1
YT1
YB1
XR1
VSS
_OSCOUT
OSCIN
9
8
ScreenCoder, MouseCoder and Self-Power
Management are a trademark of Semtech Corp.
All other trademarks belong to their respective
companies.
Copyright Semtech 2000-2001
DOC7-TS2-S840-DS-102
1
www.semtech.com






UR7HCTS2-S840-FG Datasheet, Funktion
TOUCH SCREEN SENSOR INTERFACE (CON’T)
Touch Measurement
Position information is only collected if it has been determined that the touch pressure is sufficient for an accurate
reading. To obtain position information from the Resistive Touch Screen Sensor, the ScreenCoderTM SPI/Serial uses
four internal drivers (two pins for each driver) and four sense lines. During sampling, the drivers of the X-axis are
activated by setting one X-drive high and the other X-drive low. The drivers for Y-axis are set floating. This action
produces a voltage gradient across the touch screen's surface in the X direction. The internal A/D measures both
the voltage across the activated X-plane and the voltage potential between the planes. Next, the drivers for the Y-
axis are activated while the drivers for X-axis are set floating. Again, the internal A/D measures both voltage across
the activated plane and potential between the planes. The X and Y absolute position is obtained from these four
A/D measurements. The IC keeps measuring the touch pressure even while the positioning data is acquired. If
insufficient touch pressure is detected during sampling of the position, the current data set will be rejected.
Touch algorithm
Due to vibration and electrical noise, the raw data can not be used directly. Internal data processing delivers
consistent position accuracy and quick touch response.
Resolution
The ScreenCoderTM SPI/Serial uses a built-in A/D converter to get the touch position. The maximum absolute
position resolution is 1000 points per direction. Resolution varies somewhat for different touch screen sensors, due
to voltage droop on connecting wires and sensor’s mechanical construction.
Touch screen from different makers
Operating parameters for the touch screens from different manufacturers vary depending on the size of the sensor,
material it is made from, and mechanical construction. The ScreenCoderTM SPI/Serial takes these properties into
account, and adjusts automatically for plate-to-plate capacitance, intrinsic plate resistances, etc.
Touch-screen's coordinates
The zero point for the touchscreen is at the left upper corner. See the diagram (0,0)
to the right.
X
Buttons
The ScreenCoderTM SPI/Serial implements left and right buttons. The buttons
information is combined with external mouse's buttons information when it is
sent to the system. Typically, the buttons are not used, they are provided as a
development aid.
Y
Copyright Semtech 2000-2001
DOC7-TS2-S840-DS-102
6
www.semtech.com

6 Page









UR7HCTS2-S840-FG pdf, datenblatt
SUGGESTED INTERFACING FOR THE SCREENCODERTM SPI/SERIAL UR7HCTS2-S840-FG IN SPI MODE
Copyright Semtech 2000-2001
DOC7-TS2-S840-DS-102
12
www.semtech.com

12 Page





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