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参数资料
| 型号： | MC44BC374C |
| 厂商： | Motorola, Inc. |
| 英文描述： | PLL Tuned UHF and VHF Audio/Video High Integration Modulator |
| 中文描述： | 锁相环调谐UHF和VHF音频/视频高集成调制器 |
| 文件页数： | 19/30页 |
| 文件大小： | 915K |
| 代理商： | MC44BC374C |
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Modulator Description
MOTOROLA
MC44BC373C/374C Technical Data
For More Information On This Product,
Go to: www.freescale.com
19
13.8
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 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 given by:
with:
Programming a division-ratio N=0 is not allowed.
13.9
Logic Output Port
The LOP pin is used to control any logic function. The primary applications are to control an external
attenuator or an external switch, between the antenna input and TV output.
A typical attenuator application with PIN diode is shown. The LOP pin is used to switch the PIN
attenuator depending on the signal strength of the Antenna Input, thereby reducing the risks of
Intermodulation in certain areas. The LOP may also be used as an OFF position bypass switch or for other
logic functions in the application.
Figure 6. Attenuator Application with PIN Diode
13.10
Video Section - Peak White Clip
The modulator requires the following:
A composite video input with negative going sync pulses
A nominal level of 1Vp-p
This signal is AC-coupled to the video input where the sync tip level is clamped.
The video signal is then passed to a Peak White Clip circuit. The PWC circuit function is to soft-clip the
top of the video waveform if the “sync tip amplitude” to “peak white clip” goes too high. This method
avoids carrier over-modulation by the video. Clipping can be disabled by software.
N
F
8
---
4
128
×
=
N
2048
N
11
×
1024
N
10
×
……
4
N
2
×
2
N
1
×
N
0
+
+
+
+
+
=
LOP pin
Vcc
TV Out
Antenna
Input
F
Freescale Semiconductor, Inc.
n
.
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相关代理商/技术参数 |
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| MC44BC374CD | 制造商:MOTOROLA 制造商全称:Motorola, Inc 功能描述:PLL Tuned UHF and VHF Audio/Video High Integration Modulator |
| MC44BC374CDR2 | 制造商:FREESCALE 制造商全称:Freescale Semiconductor, Inc 功能描述:PLL Tuned UHF and VHF Audio/Video High Integration Modulator |
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| MC44BC374CDTBR2 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| MC44BC374CED | 制造商:Motorola Inc 功能描述: |
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