TDA9141 datasheet(6/25 Pages) PHILIPS

6 / 25 page

December 1992

Philips Semiconductors

Product speciﬁcation

PAL/NTSC/SECAM decoder/sync

processor

TDA9141

FUNCTIONAL DESCRIPTION

General

The TDA9141 is an I2C-bus

controlled, alignment-free

PAL/NTSC/SECAM colour

decoder/sync processor which has

been designed for use with baseband

chrominance delay lines.

In the standard operating mode the

I2C-bus address is 8A. If the address

input is connected to the positive rail

the address will change to 8E.

Input switch

WARNING: THE VOLTAGE ON THE

CHROMINANCE PIN MUST NEVER

EXCEED

5.5 V. IF IT DOES THE IC

ENTERS A TEST MODE

The TDA9141 has a two pin input for

CVBS or YC signals which can be

selected via the I2C-bus. The input

selector also has a position in which it

automatically detects whether a

CVBS or YC signal is on the input. In

this input selector position, standard

identification first takes place on an

added Y/CVBS and C input signal.

After that, both chrominance signal

input amplitudes are checked once

and the input with the strongest

chrominance burst signal is selected.

The input switch status is read out by

the I2C-bus via output bit YC.

CVBS output

In the standard operating mode with

the I2C-bus address 8A, a CVBS

output signal is available on the

address pin, which represents either

the CVBS input signal or the Y/C input

signal, added into a CVBS signal

RGB colour matrix

WARNING: THE VOLTAGE ON THE UIN

PIN MUST NEVER EXCEED

5.5 V. IFIT

DOES THE

IC ENTERS A TEST MODE.

The TDA9141 has a colour matrix to

convert RGB input signals into YUV

signals. A fast switch, controlled by

the signal on pin F and enabled by the

I2C-bus via EFS (enable fast switch),

can select between these YUV

signals and the YUV signals of the

decoder. The Y signal is internally

connected to the switch. The

−(R−Y)

and

−(B−Y) output signals of the

decoder have to first be delayed in

external baseband chrominance

delay lines. The outputs of the delay

lines must be connected to the UV

input pins. If the RGB signals are not

synchronous with the selected

decoder input signal, clamping of the

RGB input signals is possible by

I2C-bus selection of STM (search

tuning mode), EFS and by feeding an

external clamping signal to the CLP

pin.

Also in search tuning mode the VA

output will be in a high impedance

OFF-state.

Standard identiﬁcation

The standards which the TDA9141

can decode are dependent on the

choice of external crystals. If a

4.4 MHz and a 3.6 MHz crystal are

used then SECAM, PAL 4.4/3.6 and

NTSC 4.4/3.6 can be decoded. If two

3.6 MHz crystals are used then only

PAL 3.6 and NTSC 3.6 can be

decoded. Which 3.6 MHz standards

can be decoded is dependent on the

exact frequencies of the 3.6 MHz

crystals. In an application where not

all standards are required only one

crystal is sufficient (in this instance

the crystal must be connected to the

reference crystal input (pin 30)). If a

4.4 MHz crystal is used it must always

be connected to pin 30. Both crystals

are used to provide a reference for

the filters and the horizontal PLL,

however, only the reference crystal is

used to provide a reference for the

SECAM demodulator.

To enable the calibrating circuits to be

adjusted exactly two bits from I2C-bus

subaddress 00 are used to indicate

which crystals are connected to the

IC.

The standard identification circuit is a

digital circuit without external

components; the search loop is

illustrated in Fig.3.

The decoder (via the I2C-bus) can be

forced to decode either SECAM or

PAL/NTSC (but not PAL or NTSC).

Crystal selection can also be forced.

Information concerning which

standard and which crystal have been

selected and whether the colour killer

is ON or OFF is provided by the read

out. Using the forced-mode does not

affect the search loop, it does,

however, prevent the decoder from

reaching or staying in an unwanted

state. The identification circuit skips

impossible standards (e.g. SECAM

when no 4.4 MHz crystal is fitted) and

illegal standards (e.g. is forced

mode). To reduce the risk of wrong

identification PAL has priority over

SECAM (only line identification is

used for SECAM).

Integrated ﬁlters

All filters, including the luminance

delay line, are an integral part of the

IC. The filters are gyrator-capacitor

type filters. The resonant frequency of

the filters is controlled by a circuit that

uses the active crystal to tune the

SECAM Cloche filter during the

vertical flyback time. The remaining

filters and the luminance delay line

are matched to this filter. The filters

can be switched to either 4.43 MHz,

4.28 MHz or 3.58 MHz irrespective of

the frequency of the active crystal.

The switching is controlled by the

identification circuit.

In YC mode the chrominance notch

filter is bypassed, to preserve full

signal bandwidth.

For a CVBS signal the chrominance

notch filter can be bypassed by

I2C-bus selection of TB (trap bypass).

The luminance delay line delivers the

Y signal to the output 60 ns after the

−(R−Y) and −(B−Y) signals have

arrived at their outputs.

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