¨

©

I

and R

¨

¨

©

I

-

¦

18

y=x+1

GAMMA_2

GAMMA_4

GAMMA_5

GAMMA_3

GAMMA_6

GAMMA_7

GAMMA_9

GAMMA_10

GAMMA_11

GAMMA_14

GAMMA_12

GAMMA_13

GAMMA_15

GAMMA_16

GAMMA_17

GAMMA_18

LM8207

14.4 V

VGMA1

VGMA2

VGMA3

VGMA16

VGMA17

VGMA18

COLUMN DRIVERS

GAMMA_1

GAMMA_8

LM8207

www.ti.com

SNOSAL5A – SEPTEMBER 2005 – REVISED MARCH 2013

•

Gamma Buffers 17-18

–

able to sink current from the resistive load of the column driver having an open collector structure. To

meet the operating voltage range, these outputs need a resistive load connected to a higher potential

sinking an output current of at least 1 mA

Example:

A typical application using the LM8207 is given in Figure 38. The corresponding gamma correction curve

(VGMA1...VGMA18) is defined in Table 1. The Voltage Reference supplies the 14.4V to the resistor network. The

calculations for the resistor values and for setting the Voltage Reference are shown in the section “Voltage

Reference.”

Figure 38. Typical TFT Display Application Diagram Using the LM8207

The values of the resistors in the gamma correction curve are calculated such that a current of 1 mA flows in the

resistor chain.

where

•

x is the index for the corresponding gamma voltage and has a range of 1 to 18

(3)

Using these formulas the resistor values in Table 1 are calculated. High accuracy resistors values can be

realized using 0.1% resistors. A method for fine-tuning the resistor value is to combine two resistors in series.

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Product Folder Links: LM8207