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Part: LM8400
Category:
Description: Four Wire Resistive Touchscreen Controller With Brownout
Company: National Semiconductor Corporation
Datasheet: Download LM8400 datasheet File size : 136 kB
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Datasheet text preview:
LM8300/LM8400/LM8500 Four Wire Resistive Touchscreen Controller with Brownout
PRELIMINARY
October 2002
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 Devices included in this datasheet: Device LM8300 LM8400 LM8500 Operating Voltage 3, 5 V 3, 5 V 5V Brownout Voltage 2.7 to 2.9 V No Brownout 4.17V to 4.5V Operating Frequency 3.27 MHz 3.27 MHz 3.27, 10 MHz I/O Pins 18 18 18 Packages 44 LLP, 44 PLCC, 48 TSSOP 44 LLP, 44 PLCC, 48 TSSOP 44 LLP, 44 PLCC, 48 TSSOP Temperature 0°C to +70°C 0°C to +70°C 0°C to +70°C self-power down mode, the current drawn is typically less than 2 µA. 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 SHUTDOWN 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.
Features
KEY FEATURES n Supports 4 wire resistive touch panels n Low power standby current typically less than 2 µA 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
COP8TM is a trademark of National Semiconductor Corporation.
© 2002 National Semiconductor Corporation
DS200372
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LM8300/LM8400/LM8500
Block Diagram
20037201
* This pin is available in the LM8500. It is unused in the LM8300/LM8400.
Ordering Information
Part Numbering Scheme LM 8300 Family and Feature Set Indicator 8300 = Low Brownout Voltage 8400 = No Brownout 8500 = High Brownout Voltage H No. Of Pins H = 44 Pin I = 48 Pin VA Package Type LQ = LLP MT = TSSOP VA = PLCC 9 Temperature 9 = 0 to +70°C
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LM8300/LM8400/LM8500
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
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