TDA8501 View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

TDA8501

PAL/NTSC encoder

Philips Electronics 

Philips Semiconductors

PAL/NTSC encoder

Preliminary specification

TDA8501

FUNCTIONAL DESCRIPTION

The TDA8501 device comprises:

• encoder circuit

• oscillator and filter control

• sync separator and pulse shaper.

Within this functional description, the term Y is used to

describe the luminance signal and the terms U and V

respectively, are used to describe the colour difference

signals.

Encoder circuit

INPUT STAGE

The input stage of the device uses two signal paths (see

Fig.1). Fast switching between the two signal paths is

achieved by means of the signal path selection switch

MCONTROL (pin 2).

R, B AND G INPUT SIGNALS PATH

One signal path provides the connection for R, G and B

signal inputs (via pins 7, 9 and 11) which are connected to

a matrix via clamping and line blanking circuits. The signal

outputs from the matrix are U, V and Y.

For an EBU colour bar of 75% the amplitude of the signal

must be 0.7 V (peak-to-peak):

U = 0.493 (B−Y)

V = 0.877 (R−Y)

Y = 0.299 R +0.587 G +0.114 B

The Y input signal (via pin 5) differs from other signal

inputs, in that the timing of the internal clamp is after the

sync period.

The amplitude and polarity of these colour difference and

luminance input signals are processed to provide suitable

switch inputs of U, V and Y signal values.

The condition for 75% colour bar is:

pin 1

pin 3

pin 5

−(R−Y) = 1.05 V (peak-to-peak)

−(B−Y) = 1.33 V (peak-to-peak)

Y = 1 V (peak-to-peak) without sync

When selected (via MCONTROL), the U and V signals (via

the switch) are routed to the low pass filters. The Y signal

(via the switch) is routed via the adder and buffer to pin 22

(Y +SYNC OUT to delay line). Dependent on pin 17

conditioning, the Y signal may have external or internal

sync added (see section Four level control pin).

FOUR LEVEL CONTROL PIN

The Y input signal (via pin 5) is conditioned by use of the

4-level control pin (pin 17) to emulate either the PAL or

NTSC modes, with sync and input blanking off or without

sync and input blanking on.

Pin 17 may be hard wire connected to either ground (LOW

for PAL mode) or VCC (HIGH for NTSC mode). External

resistors can further modify the voltage level input at pin 17

to condition (pin 5) Y with sync and input blanking off or Y

without sync and input blanking on. (see section

PAL/NTSC and Y/Y +SYNC).

When selected (via MCONTROL), the U, V signals from

the matrix are routed through the selection switch to the

low pass filters. The Y signal from the matrix is routed

through the selection switch to the adder and combined

with the sync pulse from the sync separator and then

connected via a buffer internally to pin 22 (Y + SYNC OUT

to delay line).

−(R−Y), −(B−Y) AND Y INPUT SIGNALS PATH

A second signal path provides the connection for negative

colour difference signal inputs −(R−Y), −(B−Y) i.e. V, U (via

pins 1, 3) and luminance Y (via pin 5), which are routed

directly to the switch inputs via clamping and line blanking

circuits.

U AND V SIGNALS

In PAL and NTSC modes the U and V (colour difference)

signals at the output of the switch are configured differently

as follows:

PAL mode:

• after the adding of the burst pulse to U and V, these

signals are connected to the input of the low pass filters.

During the vertical sync period the burst pulse is

suppressed.

NTSC mode:

• the burst pulse is only added to U and the gain of the U

and V signals is 0.95 of the gain in PAL mode. During

the vertical sync period the burst pulse is suppressed.

April 1993

6

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