MC44BC375U Datasheet, PDF (3/16 Pages) Freescale Semiconductor, Inc – PLL Tuned VHF (Channel 3 / 4)Audio / Video Modulator

FUNCTIONAL OVERVIEW
Figure 2 shows a simplified block diagram of the
MC44BS375U and MC33BS375UA devices.
There are two main sections:
1. A PLL section to synthesize the VHF output channel
frequency for channel 3 or channel 4.
2. A modulator section which accepts audio and video
inputs and modulates the VHF carrier.
The high frequency BiCMOS technology allows integration
of the VHF tank circuit and certain filtering functions eliminat-
ing the need for a number of external components.
VIDEO_IN
10
SPLLFLT
8
RFOV_{CC 14}
75Ω
RF_OUT 13
LOP
3
Power
save Psave/ 9
LOP
Sound Freq
Select
— SFS
16
Channel Select
— CHS
1
Video
Modulator
LPF
Peak
White Clip
Clamp
31.25 kHz
Sound
PFD
MODULATOR
SECTION
Sound
Oscillator
and FM
Modulator
Audio
Amplifier
LPF
Sound
Modulator
Prog.
Divider
LPF ALC
7 ^AUDIOIN
6 ^PREEM
11 ^VCC
5 GND
Picture-Sound
2
Select
— PSS
VHF Divider
÷8
Prescaler
÷8
UHF
OSC.
Prog.
Divider
VCO & PLL
SECTION
Phase ^{31.25 kHz} Ref Divider
Comp.
÷128
4 MHz
XCO
12
15
GND
PLLFLT
4
XTAL
Figure 2. MC44BS375U/UA Simplified Block Diagram
POWER SUPPLY
The two device V_CCS (pins 11 and 14) must be applied at
the same time to ensure all internal blocks are correctly bi-
ased. Do NOT bias any other pin before V_CC is applied to the
device.
STANDBY MODES
During standby mode, the modulator is switched to low
power consumption. The sound oscillator, UHF oscillator and
VHF dividers, video and sound modulator sections bias are
internally turned OFF.
The modulator is programmed in standby mode when
pin 9, PSave/LO, is set to a “LO” level (see “Pin Selection” on
page 4).
LOGIC OUTPUT PORT
The Logic Output Port is used to control an external switch
(such as an antenna switch or an attenuator). This pin is an
open collector transistor able to sink up to 15 mA at a low volt-
age.
The LOP output is switched between a “HI” and “LO” level
with pin 9, Psave/LO (see “Pin Selection” on page 4).
Application Specific Products
Freescale Semiconductor
MC44BC375U
3