MC44BC373 MOTOROLA [Motorola, Inc], MC44BC373 Datasheet - Page 17

• Manufacturer Part Number: MC44BC373
• Description: Multi-Standard or PAL/ NTSC Modulator with integrated antenna booster/splitter ICs
• Manufacturer: MOTOROLA [Motorola, Inc]

The auxiliary audio input adds a sound subcarrier to the main carrier. The input can be a modulated
NICAM carrier or a second sound subcarrier for a stereo system. Pin 12 is directly connected to the sound
modulator input and the picture-to-sound ratio (P/S Ratio) depends on the auxiliary audio input level. (P/S
ratio is 20dB for 35mVrms typical.)
12.10 Test Pattern Generator
A simple test pattern is generated on the IC which can be switched in under bus control to permit a TV
receiver to easily tune in to the modulator output. The pattern consists of two white vertical bars on a black
background and a 976Hz audio test signal.
12.11 PLL Section
The reference divider is a fixed divide-by-128, resulting in a reference frequency of 31.25KHz with a
4.0MHz crystal. The 31.25KHz reference frequency is used for both UHF and Sound PLLs.
The prescaler is a fixed divide by 8 and is permanently engaged.
The programmable divider’s division ratio is controlled by the state of control bits N0 to N11. The divider
ratio N for a desired frequency F (in MHz) is provided by the following formulas:
with:
12.12 UHF Oscillator—VHF Range
The UHF oscillator is fully integrated and does not require any external components. For low frequency
testing or VHF range operation (test mode 1, states 1.b to 1.c), the UHF oscillator can be internally divided
by 2, 4, 8, or 16.
MOTOROLA
Figure 10. Test Pattern Generator—(Time in Seconds)
N
Freescale Semiconductor, Inc.
0
=
TE1
For More Information On This Product,
2048 N11
TE2
10
×
MC44BC373/374 Technical Data
Go to: www.freescale.com
+
20
1024 N10
24 28
×
N
30
TIME IN µS.
=
F
-- -
8
+
×
……
128
-------- -
40
4
+
44
4 N2
×
7/10
50
+
2 N1
3/10
×
60
64
+
N0
Modulator Operation
17