Figure 3 shows a block diagram of a TFT panel. The V

COM

buffer supplies a common voltage (V

a TFT panel. In general, V

middle of the gamma voltage range. Screen performance

can be optimized by tuning the V

tion procedure. Using the LM8342, the V

procedure is simplified by elimination of the potentiometer

adjustment task. This task is currently performed at the

factory using a trimmer adjustment tool and visual inspec-

tion, when using a stable reference voltage and a

potentiometer as a voltage divider to generate the V

COM

voltage.

PRINCIPLE OF OPERATION OF THE LM8342

The LM8342 is an integrated combination of a digitally con-

trolled current sink and a non-volatile register (7 bits EE-

PROM). Writing data can be done using the I

interface. Data can be written to a volatile register and can

also be stored in the non-volatile EEPROM. A simplified

block diagram of the LM8342 is given in Figure 4.

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FIGURE 3. TFT Panel Block Diagram

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FIGURE 4. Block Diagram of the LM8342

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