Philips TDA8505-N2, TDA8505-N1 Datasheet

DATA SH EET

Preliminary speciﬁcation Supersedes data of May 1993 File under Integrated Circuits, IC02

July 1994

INTEGRATED CIRCUITS

Philips Semiconductors

TDA8505

SECAM encoder

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Philips Semiconductors Preliminary speciﬁcation

SECAM encoder TDA8505

FEATURES

• Two input stages, R, G, B and Y, −(R−Y), −(B−Y) with multiplexing.

• Chrominance processing, highly integrated, includes vertical identification, low frequency pre-emphasis and high frequency pre-emphasis (anti-Cloche) and bandpass filter.

• Fully controlled FM modulator which produces a signal in accordance with the SECAM standard without adjustments.

• Two reference oscillators, one for D'R f

(4.40625 MHz) and one for D'B f0 (4.250 MHz). These oscillators are tuned by PLL loop with the frequency of the line sync as reference. Crystal tuning, or tuning by external reference source, of the reference oscillators is possible.

• Output stages, CVBS and separated Y + SYNC and CHROMA. For CVBS output, signal amplitude 2 V (p−p) nominal, thus only an external emitter follower is required for 75 Ω driving.

• Sync separator circuit and pulse shaper, to generate the required pulses for the processing, line, frame, FH/2 and chrominance blanking.

• A 3-level sandcastle pulse is generated for PAL/NTSC to SECAM transcoding.

• FH/2 input for locking with another decoder.

• Colour killing on the internal colour difference signals.

• Internal bandgap reference.

GENERAL DESCRIPTION

The TDA8505 is a highly integrated SECAM encoding IC that is designed for use in all applications that require transformation of R, G and B signals or Y, U and V signals to a standard SECAM signal.

The specification of the input signals is fully compatible with those of the TDA8501 PAL/NTSC encoder.

ORDERING INFORMATION

TYPE NUMBER

PACKAGE

PINS PIN POSITION MATERIAL CODE

TDA8505 32 SDIP32 plastic SOT232-1

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Philips Semiconductors Preliminary speciﬁcation

SECAM encoder TDA8505

BLOCK DIAGRAM

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MLA951 - 3

PULSE

GENERATOR

PHASE

DETECTOR

272

DIVIDER

4.25 MHz

VCO

SYNC

SEPARATOR

SWITCH

PHASE

DETECTOR

282

DIVIDER

4.406 MHz

VCO

FRAME

IDENTI-

FICATION

CLAMP

ADDER

GAIN

LIMITER

MODULATOR

PHASE

SWITCH

LOW-PASS

FILTER

LF PRE-

EMPHASIS

CHROMINANCE

BLANKING

RED

input

CL/BL

GREEN

input

CL/BL

BLUE

input

CL/BL

MATRIX

SWITCH

SEQUENCE

CL/BL CL/BL CL/BL

(R Y)

(B Y)

colour difference

inputs

luminance

input

multiplexer

control input

TEST

ref

FADJ

reference

voltage

output

FLT output

FILTER

CLOCHE BANDPASS

ADDER

chrominance

output

CVBS 2 V (p p)

output

220

BUFFER

2 kΩ

notch

output

Y+SYNC

1 V (p p)

DELAY

LINE

650

PHASE

DETECTOR

LPFDB output

PHASE

DETECTOR

LPFDR output

ADDER

VCO4.25

output

control input

(Y/Y SYNC)

sandcastle

output

FH/2 input

colour killing

input

22 nF

composite

sync

input

SSD

DDD

SSA

DDA

47 µF

100 nF

XTAL/PLL

VIDENT

input

LPF4.25

output

LPF 4.4

output

TDA8505

270 pF

Y+SYNC output

2 V (p-p)

Y+SYNC

input

19external power

supply (V )

ext

2.2 kΩ

4.7 µF

22 nF

1.2 kΩ

4.7 µF

100 nF

1 nF

3.9 kΩ

1 µF

6.8

100 Ω

470 nF

SANDCASTLE

4.7

kΩ

1.8 kΩ

22 nF

22 kΩ

µF

Fig.1 Block diagram.

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Philips Semiconductors Preliminary speciﬁcation

SECAM encoder TDA8505

PINNING

D'R and D'B are the colour difference signals at the output of the multiplexer circuit; D'R = −1.9(R−Y) and D'B = +1.5(B−Y), for an EBU bar of 75% the amplitudes are equal.

SYMBOL PIN DESCRIPTION

−(R−Y) 1 colour difference input signal, for EBU bar of 75% 1.05 V (peak-to-peak value) MCONTR 2 multiplexer control; input HIGH = RGB, input LOW = −(R−Y), −(B−Y) and Y

−(B−Y) 3 colour difference input signal, for EBU bar of 75% 1.33 V (peak-to-peak value) FH/2 4 line pulse input divided-by-2 for synchronizing two or more encoders; when not used this

pin is connected to ground Y 5 luminance input signal 1 V nominal without sync TEST 6 test pin; must be connected to V

(pin 8), or left open-circuit R 7 RED input signal for EBU bar of 75% 0.7 V (peak-to-peak value) V

DDA

8 analog supply voltage for encoder part; 5 V nominal G 9 GREEN input signal for EBU bar of 75% 0.7 V (peak-to-peak value) V

SSA

10 analog ground B 11 BLUE input signal for EBU bar of 75% 0.7 V (peak-to-peak value) Y/Y+SYNC 12 when this control input is LOW, Y without sync is connected to pin 5, input blanking at

pin 5 is active; when input is HIGH, Y+SYNC is connected to pin 5, input blanking at pin 5

is not active LPFDR 13 modulator control loop ﬁlter output; black level of D'R = 4.40625 MHz FADJ 14 adjustment pin for 4.286 MHz of HF pre-emphasis ﬁlter LPFDB 15 modulator control loop ﬁlter output; black level of D'B = 4.250 MHz FLT 16 ﬁlter tuning loop capacitor output V

ref

17 2.5 V internal reference voltage output CHROMA 18 chrominance output, amplitude corresponds with Y+SYNC at the output of the delay line V

ext

19 external power supply for sandcastle generation; when not used this pin is connected to

ground SAND 20 3-level sandcastle output pulse CVBS 21 composite SECAM output 2 V (peak-to-peak value) nominal NOTCH 22 Y+SYNC output after an internal resistor of 2 kΩ; a notch ﬁlter can be connected Y+SYNC IN 23 Y+SYNC input, connected to the output of the delay line LPF4.4 24 loop ﬁlter output for 4.40625 MHz reference oscillator Y+SYNC OUT 25 Y+SYNC output, 2 V (peak-to-peak value) nominal, connected to the input of the

delay line XTAL/PLL

VIDENT

26 control pin; input HIGH = crystal tuning, input LOW = PLL tuning, both without vertical

identiﬁcation, 2.5 V = PLL tuning with vertical identiﬁcation VCO4.25 27 when used for PLL tuning a capacitor is connected; when used for crystal tuning a crystal

has to be connected (in series with a capacitor) COLKIL 28 colour killing; input HIGH = active, internal colour difference signals are blanked CS 29 composite sync input, 0.3 V (peak-to-peak value) nominal

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Philips Semiconductors Preliminary speciﬁcation

SECAM encoder TDA8505

SSD

30 digital ground

LPF4.25 31 loop ﬁlter output for 4.25 MHz reference oscillator; connected to pin 17 (V

ref

) when

external tuning by crystal or signal source V

DDD

32 supply voltage for the digital part

SYMBOL PIN DESCRIPTION

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1 2 3 4 5 6 7 8

9 10 11 12

13 14 15 16

32 31 30 29 28 27

MLA952 - 3

MCONTR

FH/2

TEST

DDA

DDD

LPF4.25 V

SSD CS COLKIL VCO4.25

XTAL/PLL VIDENT

LPF4.4

SSA

LPFDR

FADJ

LPFDB

FLT

ref

CHROMA

SAND

CVBS

NOTCH

Y/Y SYNC

(B Y)

Y+SYNC OUT

(R Y)

Y+SYNC IN

TDA8505

ext

Fig.2 Pin configuration.

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SECAM encoder TDA8505

FUNCTIONAL DESCRIPTION

The following three important circuits are integrated:

• Encoder circuit

• Modulator control circuit

• Sync separator and pulse shaper.

Encoder circuit

NPUT STAGE

R, G and B inputs are connected to the matrix via a clamping and a blanking circuit.

For an EBU colour bar of 75% the amplitude of the signal must be 0.7 V (peak-to-peak value). The outputs of the matrix are Y, D'R and D'B.

The second part of the input stage contains inputs for colour difference signals and a luminance signal. The condition for 75% colour bar is

−(R−Y) = 1.05 V (peak-to-peak value) at pin 1,

−(B−Y) = 1.33 V (peak-to-peak value) at pin 3 and

Y = 1 V (peak-to-peak value) without sync at pin 5. After clamping and blanking the amplitude and polarity are corrected such that the signals are equal to the signals of the matrix output. Signals are connected to a switch. Fast switching between the two input parts is possible by the multiplexer control pin (pin 2).

The Y output signal of the multiplexer is added to the sync pulse of the sync separator.

The Y input (pin 5) is different to the other 5 inputs. The timing of the internal clamping is after the sync period and there is no vertical blanking.

The input blanking of Y can be switched off by a HIGH at pin 12, and the internal sync separator signal is not added to the Y signal. In this way the Y+SYNC is allowed at pin 5 and after clamping internally connected directly to pin 25.

The colour difference signals are switched sequentially by H/2 and fed to the low frequency pre-emphasis circuit.

The colour-killing input signal at pin 28 can be used for completely blanking the internal colour difference signals at the input of the low frequency pre-emphasis filter.

LOW FREQUENCY PRE-EMPHASIS This filter is fully integrated, Fig.3 illustrates the nominal

response. The transfer is guaranteed within the illustrated area for

the whole ambient temperature range by a compensation circuit.

Fig.3 Nominal response for the low frequency pre-emphasis filter.

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MLA953 - 1

f (Hz)

(dB)

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Philips Semiconductors Preliminary speciﬁcation

SECAM encoder TDA8505

VERTICAL IDENTIFICATION After the low frequency pre-emphasis the signal is

clamped and, if desired the vertical identification sawtooth waveform can be added. The generation of the vertical identification is switched on/off by the logic level input at pin 26.

Figure 4 shows the sawtooth waveform at the input of the FM modulator with the corresponding frequency values after modulation.

Vertical identification is only possible if PLL tuning is selected.

AIN + LIMITER

The gain of this amplifier is sequentially switched, so that the amplitude of D'R is 280/230 times the amplitude of D'B (based on an EBU colour bar). The signal is limited at a lower and upper level to ensure that the FM modulator frequencies are always between 3.9 MHz and 4.756 MHz. A DC offset between D'R and D'B is added which corresponds with the limiter levels.

MODULATOR

The signal of the gain + limiter stage is fed to the FM modulator.

The modulator control adjusts the DC level at pin 13 to set the frequency of the FM signal to 4.406 MHz at the black

level of D'R. The modulator control also sets the DC level at pin 15 to adjust the FM frequency to 4.250 MHz at the black level of D'B.

At the start of every line the FM modulator is stopped and is started again by a short duration pulse of the pulse shaper. These stop/start pulses are operating such that after two lines starting in the same phase, the start phase of the third line is shifted 180 degrees. This sequence is inverted during each vertical blanking.

The FM signal is fed to the internal HF pre-emphasis filter.

HF PRE-EMPHASIS AND BANDPASS FILTER An HF pre-emphasis filter combined with a bandpass filter

is integrated. Figures 5 and 6 illustrate the frequency response. Two

resistors in series with a potentiometer at pin 14 adjusts the frequency to 4.286 MHz with a tolerance of ±20 kHz.

A tuning circuit integrated with an external capacitor connected to pin 16 guarantees a stable frequency response for the whole temperature range.

The output of the bandpass filter is connected directly to the chrominance blanking circuit.

Fig.4 Vertical identification sawtooth waveform input.

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MLA954

64 µs64 µs

3.90 MHz

4.250 MHz

4.406 MHz

4.756 MHz

frequency

after

modulation

35 kHz

D'R

D'B

18 sµ

6 sµ

15 sµ

5 sµ

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SECAM encoder TDA8505

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MLA955 - 1

f (Hz)

100

(dB)

Fig.5 Frequency response of the HF pre-emphasis and bandpass filter; H as a function of frequency (1).

Fig.6 Frequency response of the HF pre-emphasis and bandpass filter; H as a function of frequency (2).

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4.9

3.7 4.1 4.5

MLA956 - 1

3.9 4.3 4.7

f (MHz)

upper limit

nominal

lower limit

(dB)

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SECAM encoder TDA8505

CHROMINANCE BLANKING The chrominance signal is blanked by the internally

generated chrominance blanking pulse. The output of this blanking stage is connected to the chrominance and CVBS output circuits.

Y+SYNC, CVBS,

AND CHROMA OUTPUTS

The Y output signal of the matrix is added to the composite sync signal of the sync separator. The output of this adder at pin 25 is connected to the input of an external delay line which is necessary for correct timing of the Y+SYNC signal corresponding with the chrominance signal. The signal amplitude at pin 25 is 2 V (peak-to-peak value) nominal, so at the output of the delay line Y+SYNC is 1 V (peak-to-peak value).

The delay line has to be DC-coupled between pins 25 and 23 to ensure the required DC level at pin 23. The output resistor of the delay line has to be connected to pin 17 where (V

ref

= 2.5 V).

The output of the delay line is connected to pin 23 which is the input of a buffer operational amplifier. The output of the buffer operational amplifier is connected to pin 22 and to the CVBS adder stage via an internal resistor of 2 kΩ. An external notch filter can be connected to pin 22. The CVBS signal amplitude output at pin 21 is 2 V (peak-to-peak value) nominal. An external emitter follower is used to provide a 75 Ω output load.

The amplitude of the chrominance output signal which is connected to pin 18 corresponds with the Y+SYNC signal at the output of the delay line.

Modulator control circuit

The modulator control circuit has two tuning modes which are controlled by the input at pin 26:

• Tuning by line frequency

• Tuning by crystal or external signal source.

UNING BY LINE FREQUENCY

Two reference voltage controlled oscillators (VCOs) are integrated, the 4.4 MHz VCO with an internal capacitor and the 4.25 MHz VCO with an external capacitor at pin 27.

A PLL loop with divider circuits directly couples the frequencies of the two VCOs with the line frequency of the sync separator sync signal.

The loop filter for the 4.40625 MHz reference is at pin 24 and the loop filter for the 4.250 MHz reference is at pin 31.

The outputs of the 272 divider are also used for pulse shaping.

Within the vertical blanking period, another two Phase Locked Loops (PLLs) synchronizes the FM modulator during two lines with the 4.406 MHz reference VCO and during the following 2 lines with the 4.250 MHz reference VCO. The loop filters are connected to pins 13 and 15 respectively.

It is necessary to use low-leakage capacitors for these loop filters.

UNING BY CRYSTAL OR EXTERNAL SIGNAL SOURCE

When the frequency of the sync pulse at pin 29 is not stable or is incorrect it is possible to tune the FM modulator using an external 4.250 MHz crystal connected to pin 27. The 4.25 MHz loop at pin 31 has to be connected to pin 17 (V

ref

). A stable line frequency reference is generated by the 272 divider circuit which is used for the 4.406 MHz reference loop.

An external signal source, instead of a crystal, can be connected at pin 27 via a capacitor in series with a resistor.

The minimum AC current of 50 µA is determined by the resistor values (R

int+Rext

) and the output voltage of the

signal source (see Fig.7).

When crystal tuning is used no vertical identification is possible.

Crystal tuning is recommended for VTR signals.

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MSA732 - 1

1 nF

ext

I 50 A

signal

source

int

800Ω

OSCILLATOR

TDA8505

V (p-p)

Fig.7 Tuning circuit for external signal source.

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Philips Semiconductors Preliminary speciﬁcation

SECAM encoder TDA8505

Sync separator and pulse shaper

The composite sync input at pin 29 together with the outputs of the 272 divider of the 4.250 MHz reference loop are the sources for all pulses necessary for the processing.

The pulses are used for:

• Clamping

• Video blanking

• FH/2

• Chrominance blanking

• Stop/start of modulator

• Vertical identification

• Timing for the modulator control

• Sandcastle pulse shaping at pin 20.

External FH/2 at pin 4 is only necessary when two or more SECAM encoders have to be locked in the same phase. The phase of the internal FH/2 can be locked with an external FH/2 connected at pin 4. A reset of the internal FH/2 is possible by forcing pin 4 to a HIGH level. This HIGH level corresponds with D'R. Pin 4 is connected to ground when not used.

Figures 9 and 10 show the generated pulses during vertical blanking for PLL tuning or crystal tuning respectively. Figure 11 shows the pulses during line blanking.

Transcoding application

A sandcastle pulse is necessary for the PAL/NTSC demodulator (i.e. TDA4510) for transcoding PAL or NTSC to SECAM.

Most of the demodulator ICs use a sandcastle pulse with an amplitude of 12 V or 8 V. A 12 V or 8 V sandcastle is not possible with the TDA8505 because of the 5 V power supply.

To generate a 3-level sandcastle pulse at pin 20 (see Fig.8) an external supply voltage must be connected to pin 19.

The PAL or NTSC CVBS signal is connected to the composite sync input (pin 29) for PLL tuning and pulse shaping. As previously mentioned the Y input at pin 5 can be used as the Y+SYNC input for the filtered Y+SYNC PAL or NTSC signal, when pin 12 is at a HIGH level.

Fig.8 3-level sandcastle pulse.

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4.5 V 0.2 V

2.5 V 0.2 V

0.5 V

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