Mitsubishi L423FR Manuel de service télécharger pdf (Page 20)

Page 20

MODEL: L423FR

Circuit explanation

1.1.

V V

ideo circuitsideo circuits

ideo circuits

It explains the video circuits of L423FR (Monitor for LT-4260).

It corresponds to various inputs (Component, VIDEO, PC, HDMI).

It explains the composition and its function of an video circuit.

(Refer to an attached “Video block diagram of LT-4260”, regarding as the flow of video signal.)•@

1-1. Video input circuit of PC

In PC input, it is inputted into IC400 of the signal processing IC via Following IC

(A) IC203 : Analog-to-digital conversion IC (AD9888KS-170 : Analog devices)

The video signal (R, G, B) of PC input is changed into a digital signal (8 bits each) from an analog

signal. Moreover, by this IC, it has the function below besides digital conversion.

- Contrast adjustment for PC

- brightness adjustment for PC

This IC is controlled by register control of IC203 via

3.3V IIC-bus 3.3V IIC-bus

3.3V IIC-bus

to MPU(IC300)

(B) IC201 : Invert IC with the Schmidt trigger (74LCX14 : Fairchild)

It is IC which inputs the horizontal sync signal and vertical sync signal of PC input.

Since there are what has a bad rising and falling characteristic and what has low amplitude in the

sync signal outputted from PC, it is necessary to modify the waveform.

It corresponds to the above-mentioned waveform as follows by this IC.

- a bad rising and falling characteristic. : Rise-time and fall-time is carried out early.

- a waveform is noisy : It prevents that the mistaken pulse occurs by the Schmidt

circuit.

- Low Amplitude : If voltage threshold is satisfied, high level will output in

3.3V.

Since 74LCX14 is a invert circuit, if its gate pass twice and it has united polarity.

This is the IC for EDID of PC.

This IC has important information about PC input such as product code, serial number, video

specification, proposed timing, color information etc.

(D)IC202 : AND-circuit IC (SN74LVC08APW : Texas Instruments)

This IC is to disable the H, V sync signal line connected to IC which power supply is dropped while

stand-by. It can operate correctly by using this.

This is controlled by ENABLE singnal from MPU(IC300) ( L : disable)

(E)IC204 : D Flop-Flop IC(74LCX74 : Fairchild)

The role of this IC is to synchronize H sync signal and V sync signal.

For output signal of IC203, H sync is synchronized by dot-clock from IC203, but V sync is not

Synchronized by H sync. This IC uses to be operated without miss-operation.

(F)IC2A0 : Color conversion IC(M66471FP : Mitsubishi)

This IC uses to perform Color conversion function such as PerfectColor, Colorview.

(G)IC2A1 : TMDS-Transmitter IC(SII160CTG100 : SiliconImage)

This IC uses to convert signal’s specification from TTL to TMDS (differential signal).

Since the input port of latter IC (IC400: Signal processor ) could use only the TMDS input, this input

specification was united by this IC.

1-2. Video input circuit of COMPONENT

In COMPONENT input, it is inputted into IC400 of the signal processing IC via Following IC.

(H)IC5A0 : Analog-switch IC with LPF (SM5301A : NPC)

In this IC, it uses only LowPassFilter function for component signal, although it has analog-switch

function.

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Mitsubishi L423FR Manuel de service Page 20

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