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Circuit Descriptions, Abbreviation List, and IC Data Sheets

5V protection

The microprocessor can sense the absence of the +5V. The
failure must be filtered by software and put in the error buffer
for serviceability. The set must go into protection.
Because of the architectural set-up of the power supply (the
+5V supply is linked to the +5V2 standby supply of the OTC), it
is not possible to detect a complete absence of the +5V and to
signal it in software. Therefore, no software error indication will
be available when there is a complete short circuit of the +5V
supply.
What happens is this:
•

When the +5V_SW is overloaded (short circuit), this will
also overload the +5V2. The supply that feeds the OTC, the
standby supply, hiccups. As a result, the +5V2 is not
overloaded anymore and can rise again. Because of the
dip in the OTC supply voltage, the OTC will get a reset and
restarts the set. If the fault cause is still present at that start-
up, the system will restart all over and the set will be in a
hiccup mode. This is not a problem if the duty cycle is low
enough.

•

If however, the short circuit on the +5V is such that the
+5V2 supply is not overloaded and the remaining voltage
on the +5V2 is still high enough to keep the OTC alive, the
short circuit on the +5V can be detected via the ADC input
of the OTC the same way the +8V protection is
implemented. The set must also go into protection.

If a +8V or a +5V dropout is detected, the protection input
should be checked several times, every 200ms. If the
protection input is active for five consecutive times, the set
must go into protection.

DC protection (from audio amplifier)

Because of the symmetrical supply of the audio amplifier, a
DC-blocking capacitor between the amplifier and the speaker
is not necessary. However, it is still necessary to protect the
speaker for DC voltages. If a DC protection is activated, the
OTC will set the TV in protection. A specific error code is

not

generated. For a detailed description, see paragraph "Audio
Amplifier".

Protections with detection via I2C bus

DC/DC protection:

When a 3V3 supply is short-circuited, the DC/DC converter
switches "off". The FBX, EBILD, and 3D Comb have no supply
voltage and therefore will give no acknowledge. In this case,
the set goes into protection and an error code is generated
(error "55").

Feature box protection

The FBX protection is no longer available. It is replaced by a
combined protection called "DC/DC protection".

Tuner protection

The tuner is supplied by the +5V_SW, which is delivered by the
standby supply. When this supply is short-circuited, the
standby supply will hiccup. If the tuner does not acknowledge
on its I2C address for five consecutive times, the set goes into
protection and an error code is generated. Maximum time
allowed before protection: 1.5 s.

3D Comb filter protection

The 3D Comb protection is no longer available. It is replaced by
a combined protection called "DC/DC protection".

9.10 LCD Panel

9.10.1 Introduction

First, a small comparison between CRT and LCD technology:
•

Cathode Ray Tube:
–

Homogeneous surface.

–

Wide range of number of displayable pixels (limited by
bandwidth and shadow mask).

–

Wide range of number of lines (limited by deflection
characteristics).

–

Wide range of frame/field frequencies (limited by
deflection and flicker).

–

Interlaced and progressive images.

•

Liquid Crystal Display:
–

Fixed number of pixels per row.

–

Fixed number of rows.

–

Limited range of field frequencies: often 50-60 Hz,
sometimes up to 75 Hz.

–

Progressive images only: de-interlacing and scaling
necessary.

The LC300W01 from LPL (LG.Philips LCD) is a color Active
Matrix Liquid Crystal Display (AM LCD) with an integrated Cold
Cathode Fluorescent Lamp (CCFL) backlight system. The
matrix employs a-Si Thin Film Transistors (TFT) as the active
elements.
It is a transmissive type display operating in the normally white
mode. This TFT-LCD has a 30.0 inch diagonally measured
active display area with WXGA resolution (1280 horizontal by
768 vertical pixel array). Each pixel is divided into Red, Green,
and Blue sub-pixels or dots, which are arranged in vertical
stripes.
Grayscale, or the brightness of the sub-pixel color, is
determined with an 8-bit grayscale signal for each dot, thus,
presenting a palette of more than 16.7 Million (true) colors.
The panel uses an 8-bit Low Voltage Differential Signaling
(LVDS) interface.

Figure 9-16 Block diagram LCD panel

Table 9-8 Backlight connector pinning

9.10.2 LVDS Interface

LVDS offers superior performance compared to the standard
single ended signal (TTL). It is even "protocol independent" so
it requires no software.

Pin

Symbol

Description

GND

Ground

Bright-Adjust 0V (Min), 5V (Max)

GND

Ground