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ADD8702

12-Channel Gamma Buffers

PANEL

TIMING

CONTROLLER

TIMING AND CONTROL

SCAN DRIVER CONTROL

GAMMA

REFERENCE

VOLTAGES

GAMMA

R

384

SOURCE DRIVER

NO. 1

768

SCAN

DRIVERS

TFT COLOR PANEL

1024

768

384

SOURCE DRIVER

NO. 2

384

SOURCE DRIVER

NO. 8

ADD8702

G

B

Figure 1. Typical SVGA TFT LCD Application

FUNCTIONAL BLOCK DIAGRAM

GND

VGMA6

VGMA5

VGMA4

VGMA3

VGMA2

VGMA1

24

23

22

21

20

19

18

17

9

10

11

12

13

14

15

16

32

31

30

26

28

27

26

25

1

2

3

4

5

6

7

8

FEATURES

Programmable 12-Channel Gamma Reference Generator

Continuous Output Current: 10 mA

Outputs with Fast Settling Time for Load Change

Output Pins Are Compatible with ADD8701

Single-Supply Operation: 7 V to 16 V

Supply Current: 15 mA Max

APPLICATIONS

TFT LCD Panels

GENERAL DESCRIPTION

The ADD8702 is a low cost, mask programmable, 12-channel

part is designed to provide gamma correction for high resolution

mask programmable to 0.3% resolution using the on-chip 500

chain resistor string. This reduces component and board costs.

The ADD8702 provides a complete programmed set of gamma

voltage references for the LCD source drivers. These references

high capacitive loads and can source or sink 250 mA peak cur-

trim-potentiometer or discrete resistors.

The output pins are compatible with the ADD8701. This allows

for single board design and fast turns for prototyping using the

initial ADD8701 board design.

The ADD8702 is specified over the temperature range of –40

°C

to +85

°C and comes in the 32-lead lead frame chip scale pack-

age (LFCSP) for compact board space.