TDA8822T PHILIPS [NXP Semiconductors], TDA8822T Datasheet - Page 21

• Manufacturer Part Number: TDA8822T
• Description: Universal I2C-bus programmable RF modulator
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
Application design
In the design of the application, it is highly recommended to separate the part of the RF oscillator as much as possible
from the part of the RF outputs in order to avoid parasitic coupling between these two parts.
A good solution is shielding the RF oscillator part to avoid radiation from and to this part. The pin OGND must be
connected to the shielding box and to ground.
The frequency range the IC covers is fixed by the choice of the components marked with a note (1) in Fig.7. For these
components, it is recommended to use the values indicated in Table 11.
Table 11 Components to be used for the RF oscillator
Video input (pin 24)
The video input level on the IC is of 500 mV (p-p). In most
of the cases, the available video signals are of 1 V (p-p)
with a source impedance of 75 .
To handle this kind of signal, we use a resistive divider with
two 470
1 V (p-p) signal down to 500 mV (p-p). In order to get an
input impedance of 75 , a resistor of 82
in parallel to the divider (R26 in Fig.7).
Audio pre-emphasis
The capacitor C22 connected in parallel with R27 is
defining the time constant for the pre-emphasis following
Table 12.
Table 12 Choice of the pre-emphasis constant
Note
1. This mode has to be considered if the pre-emphasis is
1997 Jan 08
BAND
VHF1
VHF3
special; note 1
Universal I
modulator
UHF
STANDARD
applied else-where on the path of the audio signal, or
if there is no need for pre-emphasis in specific
applications. Note also that the pre-emphasis can be
done by connecting a capacitor between pin
PREEMPH (pin 3) and ground. The value for this
capacitor is 10 nF for PAL and 15 nF for NTSC.
NTSC
PAL
resistors (R24 and R25 in Fig.7) to divide the
130 to 350 MHz
470 to 860 MHz
47 to 130 MHz
FREQUENCY
RANGE
2
C-bus programmable RF
CAPACITOR
no capacitor
330 pF
220 pF
C22
C4, C5, C7, C8
VALUE FOR
5.6 pF
4.7 pF
1.8 pF
CONSTANT
is implemented
75 s
50 s
TIME
FOR C6
VALUE
100 pF
150 pF
22 pF
21
Audio input (pin 22)
The IC is sensitive to 45 mV (p-p) on pin AUDIO and the
DC voltage on this pin is close to 0 V.
This pin needs to be grounded through a 12 k resistor
(R22 in Fig.7). Care must then be taken if a coupling
capacitor needs to be implemented on the audio path to
connect it between the signal source and the input, with
the resistor of 12 k still connected to the AUDIO pin.
NICAM input (pin 21)
The NICAM pin is sensitive to 150 mV (p-p) to reach a
level between picture carrier and NICAM carrier of typical
It is possible to put on this pin either a NICAM modulated
carrier for a NICAM application or a frequency modulated
carrier for the stereo system with a second FM carrier used
e.g. in Germany.
In a specific application where the main sound subcarrier
would be generated outside the IC, it is also possible to
inject the main sound carrier to this pin, with a level
depending on the wanted P/S. In this event, it is necessary
to stop the internal sound oscillator by setting RF0 to
logic 0 and TPSG to logic 1 (see Table 8).
20 dBc.
BB132
BB133
BB134
D1
L1: NUMBER
OF TURNS
14.5
4.5
1.5
DIAMETER
L1:COIL
3.0 mm
3.0 mm
2.5 mm
Preliminary specification
TDA8822
DIAMETER
L1: WIRE
0.3 mm
0.4 mm
0.5 mm