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LM8300/LM8500
Four Wire Resistive Touchscreen Controller with
Brownout
1.0 General Description
The LM8300/8500 is a 4-wire resistive touch screen control-
ler. The controller samples and drives the touch screen
without the need of any external hardware. The built in 10-bit
A/D provides a maximum of 500 coordinate pairs per second
(cpps). The data sampled from the touch screen is sent out
on the UART at a speed of 38400 bps.
The controller has a power-saving mode which causes the
controller to self-power down when no touch is detected on
the touch screen for a specified amount of time. In the
self-power down mode, the current drawn is typically less
than 2 A. The device resumes normal operation when a
touch is detected on the touch screen or communication is
detected on the UART. In addition to the self-power down
mode, the controller can be disabled by pulling the SHUT-
DOWN pin low. The controller resumes normal operation
when the SHUTDOWN pin is tristated or pulled high.
The controller has an internal non-volatile memory storage
element to store configuration data such as calibration points
or controller configurations.
Devices included in this datasheet:
Device
Operating
Voltage
Brownout
Voltage
Operating
Frequency
I/O
Pins
Packages
Temperature
LM8300
3, 5 V
2.7 to 2.9 V
3.27 MHz
18
44 LLP, 44 PLCC,
48 TSSOP
0C to +70C
LM8500
5 V
4.17V to 4.5V
3.27, 10 MHz
18
44 LLP, 44 PLCC,
48 TSSOP
0C to +70C
2.0 Features
KEY FEATURES
n
Supports 4 wire resistive touch panels
n
Low power standby current typically less than 2 A at
5.5V
n
Maximum speed of 500 coordinate pairs per second
n
Automatic wake up and return to standby
n
10 bit A/D
n
On-chip touch screen current drivers - no external driver
required
n
UART interface
n
Controller configurations are stored in the internal
non-volatile storage element
n
Touch pressure can be measured
APPLICATIONS
n
Personal Digital Assistants
n
Smart Hand-Held Devices
n
Touch Screen Monitors
n
Point-of-Sales Terminals
n
KIOSK
n
Pagers
n
Cell Phones
COP8 is a trademark of National Semiconductor Corporation.
PRELIMINARY
December 2003
LM8300/LM8500
Four
W
ire
Resistive
T
ouchscreen
Controller
with
Brownout
2004 National Semiconductor Corporation
DS200372
www.national.com