LM8342

Programmable TFT V

Memory

General Description

The LM8342 is an integrated combination of a non-volatile

register (7 bits EEPROM) and a DAC controlled current

source. Using the LM8342, the V

is simplified by elimination of the potentiometer adjustment

task. This adjustment task is currently performed at the

factory using a trimmer adjustment tool and visual inspec-

tion.

The V

tion, using the I

can physically view the screen head-on (frontal viewing)

when performing this step, easing manufacturing especially

for large TFT panels.

The V

and R2) and is buffered by the actual V

controlling the level of I

The current level at the output of the LM8342 is a fraction

(1/128 to 128/128) of a maximum current which is set by

R

determined by the 7-bit DAC. As a result, the output current

of the LM8342 has a good temperature stability yielding a

very stable V

the LM8342 is done via its I

actual DAC setting is stored in a volatile register. Using a

“Write to EE” command the data can be stored permanently

in the embedded EEPROM. At power on of the device, the

EEPROM data is copied to the volatile register, setting the

DAC. At any time, the data in the EEPROM can be changed

again via the I

Features

n

I

current

n

Guaranteed monotonic DAC

n

Non-volatile memory to hold the setting

n

EEPROM in system programmable

n

No external programming voltage required

n

Maximum interface bus speed is 400 kHz

n

LLP-10 Package

Applications

n

TFT panel factory calibration

n

Digital potentiometer

n

Programmable current sink

Typical Application

20139201

November 2005

© 2005 National Semiconductor Corporation

DS201392

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