ur7hcts2-s840 Semtech Corporation, ur7hcts2-s840 Datasheet - Page 4

• Manufacturer Part Number: ur7hcts2-s840
• Description: High-performance, Low Power Touch Screen Controller/digitizer - Semtech Corporation
• Manufacturer: Semtech Corporation

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
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.
The ScreenCoder
System-coordinated Power Management.
Self-Power Management
Self-Power Management
results in the lowest power consumption possible within the present parameters of its operation. Through Self-
Power Management
system. Self-Power Management
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
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.
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.
Copyright Semtech 2000-2001
DOC7-TS2-S840-DS-102
FUNCTIONAL DESCRIPTION
EXTERNAL PS/2 INTERFACE
POWER MANAGEMENT
OSCILLATOR
Figure 1: Self-Power Management
TM
SPI/Serial implements two power management methods: Self-Power Management
TM
, the IC is capable of typically operating at only 1uA, independently of the state of the Host
TM
TM
is a method implemented by the IC that, independently of any system intervention,
offers three modes of operation: Stop, Run and Wait. "Stop" mode is the lowest power
TM
TM
SPI/Serial .
TM
primarily determines the actual power consumption of the IC. When the host is
TM
State
4
RUN
Mouse hot plug or Data Packet,
System Request To Send,
Touch Screen activity,
Button press
1s of inactivity
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STOP
TM
and
TM