8

Analog Section

TRANSFER FUNCTION

The transfer function is:

where data is the decimal value of the 10-bit data binary

input code.

The output voltages from the EL5126 will be derived from

pins. The impedance between those two pins is about 32k

Ω.

Care should be taken that the system design holds these two

reference voltages within the limits of the power rails of the

In some LCD applications that require more than 8 channels,

the system can be designed such that one EL5126 will

provide the Gamma correction voltages that are more

provide the Gamma correction voltage more negative than

system connected in this way.

CLOCK OSCILLATOR

The EL5126 requires an internal clock or external clock to

refresh its outputs. The outputs are refreshed at the falling OSC

clock edges. The output refreshed switches open at the rising

edges of the OSC clock. The driving load shouldn’t be changed

at the rising edges of the OSC clock. Otherwise, it will generate

a voltage error at the outputs. This clock may be input or output

via the clock pin labeled OSC. The internal clock is provided by

an internal oscillator running at approximately 21kHz and can

be output to the OSC pin. In a 2 chip system, if the driving loads

are stable, one chip may be programmed to use the internal

oscillator; then the OSC pin will output the clock from the

internal oscillator. The second chip may have the OSC pin

connected to this clock source.

For transient load application, the external clock Mode

should be used to ensure all functions are synchronized

together. The positive edge of the external clock to the OSC

pin should be timed to avoid the transient load effect. The

Application Drawing shows the LCD H rate signal used, here

the positive clock edge is timed to avoid the transient load of

the column driver circuits.

After power on, the chip will start with the internal oscillator

mode. At this time, the OSC pin will be in a high impedance

condition to prevent contention. By setting pin 32 to high, the

chip is on external clock mode. Setting pin 32 to low, the chip

is on internal clock mode.

START

CONDITION

STOP CONDITION

DATA

CLOCK

V

OUT IDEAL

)

(

V

REFL

=

data

1024

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V

()

×

+

EL5126