Philips tda3868t DATASHEETS

INTEGRATED CIRCUITS

DATA SH EET

TDA3868T

Quasi-split sound processor for all
standards

Preliminary specification
File under Integrated Circuits, IC02

January 1992

Philips Semiconductors Preliminary specification

Quasi-split sound processor for all standards TDA3868T

FEA TURES

• Quasi-split sound processor for all standards e. g. B/G
(FM sound) and L (AM sound)

• Reduction of spurious video signals by tracking function

GENERAL DESCRIPTION

Separate symmetrical IF inputs for FM and AM sound.
Gain controlled wideband IF amplifier and input select

switch.

and AFC for the vision carrier reference circuit;
(indispensable for NICAM)

• AF2 signal automatically muted (at B/G) by input signal
level

• AM signal processing for L standard and audio switching
over

• Stereo-matrix correction

• AM output level typically 500 mV at m = 0.54 (+2.5 dB in

comparison to TDA3858)

AGC generation due to peak-sync for FM or mean signal
level for AM.

Reference amplifier to regenerate the vision carrier.
Limiting amplifier optimized for AM suppression of the

regenerated vision carrier signal and 90° phase shifter.
Intercarrier mixer for FM sound, output with low-pass filter.
Separate signal processing for 5.5 and 5.74 MHz

intercarriers.
Wide supply voltage range, only 300 mW power

dissipation at 5 V.

QUICK REFERENCE DATA

SYMBOL PARAMETER MIN. TYP. MAX. UNIT

V

P

Data at V

I

P

V

iIF

V

o

P

supply voltage (pin 24) 4.5 5 8.8 V

=5 V

supply current (pin 24) − 60 72 mA
IF input sensitivity (−3 dB) − 70 100 µV
audio output signal for FM standard B/G (RMS value) − 1 − V
audio output signal for AM standard L (RMS value) − 0.5 − V

THD total harmonic distortion

for FM − 0.5 − %
for AM − 1 − %

S/N (W) weighted signal-to-noise ratio

for FM − 68 − dB
for FM with 6 kHz sinus vision modulation − 56 − dB
for AM − 56 − dB

ORDERING AND PACKAGE INFORMATION

EXTENDED TYPE

NUMBER

TDA3868T 28 mini-pack plastic SOT136A

Note

1. SOT136-1; 1996 November 25.

January 1992 2

PACKAGE

PINS PIN POSITION MATERIAL CODE

(1)

Philips Semiconductors Preliminary specification

Quasi-split sound processor for all standards TDA3868T

January 1992 3

Fig.1 Block diagram (B/G and L standards).

Philips Semiconductors Preliminary specification

Quasi-split sound processor for all standards TDA3868T

PINNING

SYMBOL PIN DESCRIPTION

AMIF1 1 AM IF difference input 1 for L standard (32.4 MHz)
AMIF2 2 AM IF difference input 2 for L standard (32.4 MHz)
C

AGC

C

AM

MODE 5 3-state input for standard select
MATR 6 input for stereo matrix correction
FM2R1 7 reference circuit for FM2 (5.74 MHz)
FM2R2 8 reference circuit for FM2 (5,74 MHz)
AF2 9 AF2 output (AF out of 5.74 MHz)
AF1 10 AF1 output (AF out of 5.5 MHz or AM)
FM1R1 11 reference circuit for FM1 (5.5 MHz)
FM1R2 12 reference circuit for FM1 (5.5 MHz)
n.c. 13 not connected
VC-R1 14 reference circuit for the vision carrier (38.9 MHz)
VC-R2 15 reference circuit for the vision carrier (38.9 MHz)
TRACK 16 DC output level for tracking
C

AFAM

FM1l 18 intercarrier input for FM1 (5.5 MHz)
C

AF1

ICO 20 intercarrier output signal (5.5/5.74 MHz)
C

AF2

FM2l 22 intercarrier input for FM2 (5.74 MHz)
GND 23 ground (0 V)
V

P

n.c. 25 not connected
C

ref

FMIF1 27 IF difference input 1 (B/G standard, 38.9 MHz)
FMIF2 28 IF difference input 2 (B/G standard, 38.9 MHz)

3 charge capacitor for AGC (FM and AM)
4 charge capacitor for AM AGC

17 DC-decoupling capacitor for AM demodulator (AF AM)

19 DC-decoupling capacitor for FM1 demodulator (AF1)

21 DC-decoupling capacitor for FM2 demodulator (AF2)

24 +5 to +8 V supply voltage

26 charge capacitor for reference voltage

Fig.2 Pin configuration.

January 1992 4

Philips Semiconductors Preliminary specification

Quasi-split sound processor for all standards TDA3868T

FUNCTIONAL DESCRIPTION

The quasi-split sound processor is for
all standards. Dependent on the
voltage on pin 5 either FM mode
(B/G) or AM mode (L) is selected.

B/G standard (FM mode): Pins 27 and
28 are active, AGC detector uses
peak sync level. Sound carrier SC1
(5.5 MHz) provides AF1, sound
carrier SC2 (5.74 MHz) provides AF2.
With no sound carrier SC2 on pin 22,
AF2 output is muted (in mid-position
of the standard select switch FM
mode without muting of AF2 is
selected). The mute circuit prevents
false signal recognition in the stereo
decoder at high IF signal levels when
no second sound carrier exists
(mono) and an AF signal is present in
the identification signal frequency
range.
With 1 mV on pin 22, under
measurement conditions, AF2 is
switched on (see limiting amplifier).
Weak input signals on pins 27 and 28
generate noise on pin 22, which is
present in the intercarrier signal and
passes through the 5,74 MHz filter.
Noise on pin 22 inhibits muting. No
misinterpretation due to white noise
occurs in the stereo decoder; when
non-correlated noise masks the
identification signal frequencies,
which may be present in sustained
tone signals. The stereo decoder
remains switched to mono.

The series capacitor Cs in 38.9 MHz
resonant circuit provides a notch at
the sound carrier frequency in order
to provide more attenuation for the
sound carrier in the vision carrier
reference channel. The ratio of
parallel/series capacitor depends on
the ratio of VC/SC frequency and has
to be adapted to other TV
transmission standards if necessary,
according
to

CSCPfVCfSC⁄()

2

˙

C

P

.–=

The result is an improved “intercarrier
buzz” (up to 10 dB improvement in
sound channel 2 with 250 kHz video
modulation for B/G stereo) or
suppression of 350 kHz video
modulated beat frequency in the
digitally-modulated NICAM
subcarrier. The picture carrier for
quadrature demodulation in the
intercarrier mixer is not exactly 90
degrees due to the shift variation in
the integrated phase shift network.
The tuning of the LC reference circuit
to provide optimal video suppression
at the intercarrier output is not the
same as that to provide optimal
intercarrier buzz suppression. In
order to optimize the AF signal
performance, a fine tuning for the
optimal S/N at the sound channel 2
(from 5.74 MHz) may be performed
with a 250 kHz square wave video
modulation.

Measurements at the demodulators:
For all signal-to-noise measurements
the generator must meet the following
specifications;

phase modulation errors<0.5 degree
for B/W-jumps intercarrier
signal-to-noise ratio as measured
with “TV-demodulator AMF2”
(weighted S/N) must be > 60 dB at
6 kHz sine wave modulation of the
B/W-signal.

Signal-to-noise ratios are measured
with ∆f=±50 kHz deviation and
f

= 1 kHz; with a deviation of

m

±27 kHz the S/N ratio is deteriorated
by 5.3 dB.

L standard (AM mode): Pins 1 and 2
are active, AGC detector uses mean
signal level. The audio signal from the
AM demodulator is output on AF1
with AF2 output muted.

January 1992 5

Philips Semiconductors Preliminary specification

Quasi-split sound processor for all standards TDA3868T

LIMITING VALUES

In accordance with the Absolute Maximum System (IEC 134).

SYMBOL PARAMETER MIN. MAX. UNIT

V

P

V

I

P

tot

T

stg

T

amb

V

ESD

Note

1. Equivalent to discharging a 200 pF capacitor through a 0 Ω series resistor.

supply voltages (pin 24) − 8.8 V
voltage (pins 1, 2, 5, 9, 10, 18, 20, 22, 27 and 28) 0 V

P

V
total power dissipation 0 635 mW
storage temperature range −25 150 °C
operating ambient temperature range 0 70 °C
electrostatic handling

(1)

all pins except 1, 2, 27 and 28 ±500 − V
pins 1, 2, 27 and 28 +400 − V
pins 1, 2, 27 and 28 −500 − V

January 1992 6