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ScreenCoder

UR7HCTS2-S840

High-Performance, Low Power

Touch Screen Controller/Digitizer

ScreenCoder, MouseCoder and Self-Power
Management are a trademark of Semtech Corp.
All other trademarks belong to their respective
companies.

www.semtech.com

HID & SYSTEM MANAGEMENT PRODUCTS, MOUSECODER

FAMILY

DESCRIPTION

FEATURES

LQFP

SYT

SXL

_PWR_DOWN

SOUT

ISEL/SCLK

TxD

RSVD2

_RB

OSCIN

_OSCOUT

VSS

XR1

YB1

YT1

XL1

_RTS/_SS

SXR

XPWRS

_CTS/_ATN

VREF

_RESET

VSS2

VDD

XCLK

XDAT

RVSD1

XL2

YT2

YB2

XR2

_LB

SYB

The ScreenCoder

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 ScreenCoder

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 ScreenCoder

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 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.

· Zero-Power

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

· 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

· Wireless Internet Appliances
· Handheld PCs (H/PCs)

· Web Phones
· Portable Systems

APPLICATIONS

PIN ASSIGNMENTS

BLOCK DIAGRAM

ORDERING CODE

www.semtech.com

Package Options

Pitch in mm's

TA=-20° C to +85° C

32-pin, Plastic LQFP

0.8

UR7HCTS2-S840-FG

Other Materials

Type

Order number

ScreenCoder

SPI/Serial Evaluation

Kit

EVK7-TS2-S840-XXX

Note 1: XXX= Denotes Revision number

ASI/SPI

Communication port

Power Management

Section

Power-On Reset

16 bit Timer

Oscillator Circuit

Sensor Interface

Switch Interface

Touch Panel

Interface

8042 Emulation port

ASI/SPI

OSCIN

_OSCOUT

Left Button

Right Button

Drivers for Touch

Screen

Sense Line

XCLK

XDAT

PIN DEFINITIONS

www.semtech.com

Mnemonic

Pin #

Type

Name and Function

VDD

Power Supply

VSS

Ground

VSS2

Ground

OSCIN

Oscillator Input: external clock input or one
side of the Ceramic Resonator with built-in Load
Capacitors

_OSCOUT

Oscillator Output: open for external clock
input or other side of the Ceramic Resonator with
built-in Load Capacitors

_RESET

Reset: apply 0V to provide orderly start-up

XCLK

I/O (nd)

External Mouse Clock: PS/2 clock signal from
external mouse; keep open if unused

XDAT

I/O (nd)

External Mouse Data: PS/2 data signal from
external mouse; keep open if unused

_LB

I/O (nd)

Left Button: active low

_RB

I/O (nd)

Right Button: active low

XR1, XR2

12, 23

I/O

Sensor's Excitation Driver: connect to X Right

YB1, YB2

13, 22

I/O

Sensor's Excitation Driver:connect toY Bottom

YT1, YT1

14, 21

I/O

Sensor's Excitation Driver:connect to Y Top

XL1, XL2

15, 20

I/O

Sensor's Excitation Driver: connect to X Left

VREF

Reference Voltage for built-in A/D

SXL

Sense line: for X Left

SYT

Sense line: for Y Top

SYB

Sense line: for Y Bottom

SXR

Sense line: for X Right

_PWR_DOWN

Hardware Power Down: tie high if unused

XPWRS

External Mouse Power Sense: connect to
switched power plane for the external pointing device

or tie high if external mouse port is used; tie low if

external mouse port is unused

_SS/_RTS

Slave Select / Ready To Send: active low, host
ready to get data

_ATN/_CTS

Attention / Clear To Send: active low, request

data transfer

TXD

27 O

Data Output: Serial mode

SCLK/ISEL

Interface Select / SPI Clock: tie low for Serial

SOUT

I/O

Data Output: SPI mode

RSVD1-2

19,26

I/O

Reserved: Keep open

Note: An underscore before a pin mnemonic denotes an active low signal.
Pin Types Legend: AI=Analog Input; I=Input; O=Output; I/O=Input or Output;
I/O (nd)=Input or Output with N-channel Open Drain driver

FUNCTIONAL DESCRIPTION

www.semtech.com

The UR7HCTS2-S840 consists functionally of five major sections (see the Functional Diagram). These are the
Sensor Interface, Power Management section, the 16-Bit Timer, the Oscillator Circuit and the Serial Peripheral
Interface (SPI) and the Asynchronous Serial Interface (Serial). All sections communication with each other and
operate concurrently.

This IC has a built-in Oscillator circuit capable of operations with an external 4.00 MHz Clock source, or a Ceramic
Resonator (preferably with built-in Load Capacitors). Note, that the Crystals can NOT be used. The ScreenCoder

SPI/Serial frequently switches its Oscillator OFF and ON in order to operate with the least amount of power
consumption. Due to very high Q, the Crystal-based oscillators have exceedingly long Start-up time and can not
be used with the ScreenCoder

SPI/Serial .

RUN

STOP

System Request To Send,

Mouse hot plug or Data Packet,

Touch Screen activity,

Button press

1s of inactivity

Figure 1: Self-Power Management

State

OSCILLATOR

EXTERNAL PS/2 INTERFACE

There is one external PS/2 port for the connection of standard PS/2 devices, including a Microsoft WheelMouse or
5-Button Mouse. The mouse motion data is sent out in relative format. The external PS/2 port also supports hot-
plug; users can connect the mouse to the system at any time without rebooting.

POWER MANAGEMENT

The ScreenCoder

SPI/Serial implements two power management methods: Self-Power Management

and

System-coordinated Power Management.

Self-Power Management

is a method implemented by the IC that, independently of any system intervention,

results in the lowest power consumption possible within the present parameters of its operation. Through Self-
Power Management

, the IC is capable of typically operating at only 1uA, independently of the state of the Host

system. Self-Power Management

primarily determines the actual power consumption of the IC. When the host is

in the active state, the IC can still operate most of the time at only 1uA, even when an active external PS/2 device
is attached to it.

Self-Power Management

offers three modes of operation: Stop, Run and Wait. "Stop" mode is the lowest power

consumption mode. In this mode, the oscillator is stopped and the IC consumes only the leakage current. This is
the default mode to which the IC will revert when it is idle. "Wait" mode is entered when the IC is waiting for a
response or continuation of data stream from the PS/2 device. The duration of wait mode is limited to 40ms, within
which time the IC will either receive new data from the PS/2 device or enter "Stop" mode. Typical power
consumption in this mode is several hundred uAs. "Run" mode is entered briefly, only to process an event. The IC
will only remain in this mode when there are pending tasks, such as PS/2 report reception or initialization of the
PS/2 device.

POWER MANAGEMENT (CON'T)

www.semtech.com

Critical Suspend

Ext Mouse

power down

Normal State

_PWR_DOWN=0

_PWR_DOWN=1
and XPWRS=1

_PWR_DOWN=0

_PWR_DOWN=1
and XPWRS=1

_PWR_DOWN=1
and XPWRS=0

Figure 2: System-coordinated Power Management

System-coordinated Power
Management

Normal Operation State:

In normal operation state, both the
_PWR_DOWN and XPWRS pins are
in high state. The ScreenCoder

SPI/Serial operations are controlled
by Self-Power Management

Critical Suspend:

At any time, the Host may negate
the _PWR_DOWN pin in order to
force the ScreenCoder

SPI/Serial

into a "critical suspend" mode. This
signal can be activated (driven low)
due to specific conditions of the
Host's operations (for example, a
discharged battery), or due to
actions of the Operating System or
BIOS.

During the "critical suspend", the
ScreenCoder

SPI/Serial will shut

down all of the pointing activities.

External PS/2 power down:

The ScreenCoder

SPI/Serial

monitors the state of the power
supply rail for the external PS/2
pointing device through the XPWRS
pin. If the IC senses that the external
PS/2 device has been powered-
down by the host, it will actively
eliminate shot-through current in the
input buffers for the clock and data
lines by driving both low.

The ScreenCoder

SPI/Serial will re-

initialize the external PS/2 pointing
device when the power to the
external PS/2 port is restored.

The ScreenCoder

SPI/Serial can acquire data from any four- or eight-wire

resistive touch screen sensors. The sensor interface has the following
features:

Touch detection

The IC periodically checks touch pressure applied to the panel. If there is
no touch, the IC will not perform measurements and will not send data to
system. When touch pressure is detected, the IC further qualifies and
determines the amount of pressure. Semtech's proprietary, patent-pending
touch detection algorithm performs this test very quickly, accommodating
sensors with various plate-to-plate capacitances.

TOUCH SCREEN SENSOR INTERFACE

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ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: UR7HCTS2-S840