MC44BC373 Datasheet, PDF (17/24 Pages) Motorola, Inc – Multi-Standard or PAL/ NTSC Modulator with integrated antenna booster/splitter ICs

Freescale Semiconductor, Inc. _{Modulator Operation}
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.
TE2
7/10
3/10
TE1
0
10
20 24 2830
40 44 50
TIME IN µS.
60 64
Figure 10. Test Pattern Generator—(Time in Seconds)
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:
N = ^F-- × ^1----2---8-
84
N = 2048 × N11 + 1024 × N10 + …… + 4 × N2 + 2 × N1 + N0
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
MC44BC373/374 Technical Data
17
For More Information On This Product,
Go to: www.freescale.com