FEATURES

• I2C Compatible Programmable DAC to Set the

Output Current

• Ensured Monotonic DAC

• Non-Volatile Memory to Hold the Setting

• EEPROM in System Programmable

• No External Programming Voltage Required

• Maximum Interface Bus Speed is 400 kHz

• SON-10 Package

APPLICATIONS

• TFT Panel Factory Calibration

• Digital Potentiometer

• Programmable Current Sink

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

VCOM calibration procedure 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 inspection.

The VCOM adjustment can be done electronically in

production, using the I2C compatible interface. The

factory operator can physically view the screen headon

(frontal viewing) when performing this step, easing

manufacturing especially for large TFT panels.

The VCOM level is typically at half AVDD (determined

by R1 and R2) and is buffered by the actual VCOM

driver. By controlling the level of IOUT, the VCOM level

can be tuned. 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 RSET and an analog

reference (AVDD). The actual fraction is determined

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

the LM8342 has a good temperature stability yielding

a very stable VCOM adjustment. Controlling the DAC

setting of the LM8342 is done via its I2C compatible

interface. The 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 I2C compatible interface.