MC44BC373CD FREESCALE [Freescale Semiconductor, Inc], MC44BC373CD Datasheet - Page 19

• Manufacturer Part Number: MC44BC373CD
• Description: PLL Tuned UHF and VHF Audio/Video High Integration Modulator
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

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.
13.10 Video Section - Peak White Clip
The modulator requires the following:
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.
•
•
A composite video input with negative going sync pulses
A nominal level of 1Vp-p
N
Figure 6. Attenuator Application with PIN Diode
Freescale Semiconductor, Inc.
=
For More Information On This Product,
Antenna
2048 N11
Input
MC44BC373C/374C Technical Data
×
Go to: www.freescale.com
+
1024
LOP pin
Vcc
×
N
N10
=
F
-- -
8
+
×
……
128
-------- -
4
+
4 N2
×
+
2 N1
TV Out
×
+
N0
Modulator Description