LH1687 데이터 시트보기 (PDF) - Sharp Electronics

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LH1687

240-output TFT-LCD Source Driver IC

Sharp Electronics 

(3) Output Circuit Type

The LH1687 samples video signals by the sample

and hold circuits of 2 systems and outputs the

voltage corresponding to the sampled data by the

input switching operational amplifiers with push-pull

output buffer.

Sample and hold circuits and output circuits are as

shown in the diagram below.

LH1687

When CTR = "H", the LH1687 samples the data to

system A of the sample and hold circuits and

outputs the voltage corresponding to the voltage

sampled by capacitor B of system B.

When CTR = "L", the LH1687 samples the data to

system B of the sample and hold circuits and

outputs the voltage corresponding to the voltage

sampled by capacitor A of system A.

Video

Signal

System A of Sample and Hold Circuits

Sampling

Signal A

GNDA

Capacitor A

Capacitor B

Sampling

Signal B

GNDA

System B of Sample and Hold Circuits

Operational Amplifier

+ Output Buffer

+1

+2

–

Output Pin

Therefore, it is usually necessary to repeat the

sampling operation and output operation by

exchanging CTR signal ("H" to "L" or "L" to "H") for

every start signal.

While CTR signal is set to "H" or "L" several times

for start signal, the same voltage is output

continuously.

The output voltage corresponds to the data

sampled by the previous sampling operation.

Timing of operation is as follows.

Start signal

CTR

System A

System B

Sampling 1

Output 0

Output 1

Sampling 2

Sampling 3

Output 2

Sampling 3'

Output 2

Output 3'

Sampling 4

Also, there is a power save function which makes

high-impedance of the output pin and a reduction in

the current of operational amplifiers possible when

set to PS = "L", but careful attention must be paid

to the displaying quality etc. when using it.

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