参数资料
型号: MC44BC373
厂商: Motorola, Inc.
英文描述: Multi-Standard or PAL/ NTSC Modulator with integrated antenna booster/splitter ICs
中文描述: 多制式或PAL / NTSC制式,集成天线的助推器调制器/分路器集成电路
文件页数: 17/24页
文件大小: 635K
代理商: MC44BC373
Modulator Operation
MOTOROLA
MC44BC373/374
Technical Data
For More Information On This Product,
Go to: www.freescale.com
17
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.
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:
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.
10
20
30
40
50
60
0
64
TE1
24
28
44
TIME IN μS.
7/10
3/10
TE2
N
F
8
4
128
×
=
N
2048
N11
×
1024
N10
×
……
4
N2
×
2
N1
×
N0
+
+
+
+
+
=
F
Freescale Semiconductor, Inc.
n
.
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