LM8300/LM8400/LM8500
Four Wire Resistive Touchscreen Controller with
Brownout
General Description
The LM8300/8400/8500 is a 4-wire resistive touch screen
controller. 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
LM8400
3, 5 V
No Brownout
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
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
TM
is a trademark of National Semiconductor Corporation.
PRELIMINARY
October 2002
LM8300/LM8400/LM8500
Four
W
ire
Resistive
T
ouchscreen
Controller
with
Brownout
2002 National Semiconductor Corporation
DS200372
www.national.com
Block Diagram
20037201
* This pin is available in the LM8500. It is unused in the LM8300/LM8400.
Ordering Information
Part Numbering Scheme
LM
8300
H
VA
9
Family and Feature Set Indicator
No. Of Pins
Package Type
Temperature
8300 = Low Brownout Voltage
8400 = No Brownout
8500 = High Brownout Voltage
H = 44 Pin
I = 48 Pin
LQ = LLP
MT = TSSOP
VA = PLCC
9 = 0 to +70C
LM8300/LM8400/LM8500
www.national.com
2
Table of Contents
General Description ............................................................................................................................................ 1
Features ............................................................................................................................................................. 1
Block Diagram .................................................................................................................................................... 2
Ordering Information .......................................................................................................................................... 2
Connection Diagrams ......................................................................................................................................... 4
2.0 Pin Descriptions ........................................................................................................................................... 5
Absolute Maximum Ratings ............................................................................................................................... 7
3.0 Electrical Characteristics .............................................................................................................................. 7
4.0 Functional Description .................................................................................................................................. 8
4.1 General ...................................................................................................................................................... 8
4.2 Advanced Pin Descriptions ....................................................................................................................... 8
4.3 USART Framing Format ............................................................................................................................ 9
4.3.1. Data packet format table .................................................................................................................... 9
4.3.2 Command Bytes .................................................................................................................................. 9
4.3.3 Advanced Command Bytes Descriptions .......................................................................................... 10
5.0 Oscillator .................................................................................................................................................... 12
6.0 Power Save Mode (Low Power Stand-by) ................................................................................................ 13
7.0 Averaging Algorithm ................................................................................................................................... 13
7.1 Delta Algorithm ........................................................................................................................................ 13
7.2 Focus Algorithm ....................................................................................................................................... 13
7.3 Communication Modes ............................................................................................................................ 14
8.0 Brownout Reset .......................................................................................................................................... 14
9.0 Calibration .................................................................................................................................................. 15
9.1 General Calibration Procedures .............................................................................................................. 17
9.2 Calibration Procedures with Coordinates Checking Enabled ................................................................. 18
9.3 Calibration Procedures with Coordinates Checking Disabled ................................................................ 18
Physical Dimensions ........................................................................................................................................ 19
LM8300/LM8400/LM8500
www.national.com
3
Connection Diagrams
20037202
* This pin is available in the LM8500. It is unused in the LM8300/LM8400.
Top View
Plastic Chip Package
See NS Package Number V44A
20037203
* This pin is available in the LM8500. It is unused in the LM8300/LM8400.
Top View
LLP Package
See NS Package Number LQA44A
20037204
* This pin is available in the LM8500. It is unused in the LM8300/LM8400.
Top View
TSSOP Package
See NS Package Number MTD48
LM8300/LM8400/LM8500
www.national.com
4
2.0 Pin Descriptions
Pinouts for 44- and 48-Pin Packages
Pin Name
Direction
Pin Description
44-Pin LLP
44-Pin PLCC
48-Pin TSSOP
RESET
I
Reset pin, pull low to reset
6
1
1
DTR
I
UART Data terminal ready signal, low
if not ready
7
2
2
WD_OUT
O
Watchdog output, tie to RESET pin
for correct function
8
3
3
CLK_SET
1
I
Used to set if crystal is 3.3 MHz (low)
or 10 MHz (floating or pulled high)
9
4
4
Unused
2
10
5
5
Unused
2
11
6
6
Unused
2
12
7
7
Unused
2
13
8
8
OSC_OUT
O
Clock oscillator output
14
9
9
OSC_IN
I
Clock oscillator input
15
10
10
Unused
2
16
11
11
Unused
2
17
12
12
UART_TX
O
UART transmit pin (inverted for use
with standard RS-232 drivers)
18
13
13
UART_RX
I
UART receive pin (inverted for use
with standard RS-232 drivers
19
14
14
SHUTDOWN
I
Shutdown pin, puts the device in halt
mode if pulled low
20
15
15
Unused
2
21
16
16
Unused
2
22
17
17
WAKE-UP
I
Used to wake up the processor from
halt mode with touch on touch screen
23
18
18
X+
I/O
Drives the X+ wire, also analog input
when sampling
24
19
19
Y-
I/O
Drives the Y- wire, also analog input
when sampling
25
20
20
X-
I/O
Drives the X- wire, also analog input
when sampling
26
21
21
Y+
I/O
Drives the Y+ wire, also analog input
when sampling
27
22
22
Unused
2
28
23
23
Unused
2
29
24
24
FILTER_OUT
O
Analog output to the filter
30
25
25
FILTER_IN
I
Analog input from the filter
31
26
26
GND
Digital ground
32
27
27
AGND
Analog ground
33
28
28
AV
CC
Analog power supply, connect to filter
for best performance
34
29
31
V
CC
Digital power supply
35
30
32
Unused
2
X
X
33
Unused
2
X
X
34
Unused
2
36
31
35
Unused
2
37
32
36
Unused
2
38
33
37
Unused
2
39
34
38
Unused
2
40
35
39
LM8300/LM8400/LM8500
www.national.com
5
PDF 
ZIP