TDA8822M Philips Semiconductors, TDA8822M Datasheet - Page 6

• Manufacturer Part Number: TDA8822M
• Description: Universal I2C-bus programmable RF modulator
• Manufacturer: Philips Semiconductors

Philips Semiconductors
FUNCTIONAL DESCRIPTION
The TDA8822 is a programmable RF modulator which can
be divided into the following parts:
Video part
The video part provides the following:
1997 Jan 08
handbook, full pagewidth
Video part
Audio part
RF part.
The video part includes a clamping circuit which sets the
internal reference voltage to the bottom of the
synchronizing pulse. The modulation depth is adjusted
using 3 bits of the I
MD1 and MD0. These 3 bits make 8 different values for
the modulation depth possible (see Table 1).
After the modulation depth is set, the signal is fed
through a clip control circuit that clips the video signal to
avoid that the modulation depth becomes higher than
100%.
The video part also contains a TPSG. This TPSG
generates a pattern that helps to tune the TV set to the
programmed channel of the modulator. The pattern
consists of a sync pulse and two vertical white bars on
the screen (see Fig.3)
Universal I
modulator
2
0
C-bus programmable RF
2
C-bus programming, called MD2,
5
10
15
20
Fig.3 Test pattern signal.
25
30
35
6
Table 1 Modulation depth setting (typical values)
SETTING
The TPSG is activated in two ways:
– Forcing the pin TPSG to DGND in the application
– Setting the TPSG bit to 1 via the I
40
MD
(see Fig.8)
TPSG pin acts as an output port, sinking current to
allow the indication of the use of the TPSG in the
application e.g. with an LED (see Fig.9).
0
1
2
3
4
5
6
7
45
MD2
50
0
0
0
0
1
1
1
1
55
MD1
BIT
0
0
1
1
0
0
1
1
60
65
MD0
Preliminary specification
0
1
0
1
0
1
0
1
MGE675
t ( s)
2
C-bus, then the
TDA8822
MODULATION
DEPTH (%)
72.5
75.0
77.5
80.0
82.5
85.0
87.5
90.0