MC44BC375UAFCR2 Freescale Semiconductor, MC44BC375UAFCR2 Datasheet - Page 4

• Manufacturer Part Number: MC44BC375UAFCR2
• Description: IC MODULATOR AUD/VID VHF 20-QFN
• Manufacturer: Freescale Semiconductor
• Type: Modulatorr

Specifications of MC44BC375UAFCR2

• Applications: Set-Top Boxes
• Mounting Type: Surface Mount
• Package / Case: *
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

TRANSIENT OUTPUT INHIBIT
the UHF PLL is acquiring a lock on the desired frequency, the
Sound and Video modulators are turned OFF at power-ON
(i.e., V
from “Standby mode” to “Normal operation”).
This allows the UHF PLL to settle to its programmed frequen-
cy. During the 263 ms time-out, the sound PLL current source
is set to 10 µA typical to speed up the locking time. After the
263 ms time-out, the current source is switched to 1.0 µA.
Use care when selecting loop filter components to ensure the
loop transient does not exceed this delay.
VIDEO SECTION
ative going sync pulses and a nominal level of 1.0 V
signal is AC coupled to the video input where the sync tip lev-
el is clamped.
1.0 V
by simply adding a resistive divider at video input, resulting in
a lower signal seen by the video input stage.
whose function is to soft clip the top of the video waveform if
the amplitude from the sync tip to peak white goes too high.
In this way, over-modulation of the carrier by the video is
avoided. The clipping function is always engaged.
SOUND SECTION
require any external components. An internal low pass filter
and matched structure give a very low harmonics level.
incorporating the sound subcarrier oscillator. The audio input
signal is AC coupled into the amplifier which then drives the
modulator.
MC44BC375U
4
To minimize the risk of interference to other channels while
There is a time-out of 263 ms until the output is enabled.
The modulator requires a composite video input with neg-
The video modulation depth typical value is given for
The video signal is then passed to a peak white clip circuit
The multivibrator oscillator is fully integrated and does not
The sound modulator system consists of an FM modulator
CBVS
CC
is switched from 0 V to 5.0 V or device is switched
input level. It can be adjusted to any lower value
(pp)
. This
external capacitor C1 and an internal resistor (100 kΩ typi-
cal). The recommended capacitor value (750 pF) is for M/N
standards, time constant is 75 µs and it is 470 pF for B/G
standards (50 µs).
range, with pre-emphasis circuit engaged. Without this pre-
emphasis circuit, it is possible to extend the audio bandwidth
to high frequencies, as there is no internal frequency limita-
tion (stereo application).
PLL SECTION — DIVIDERS
ence frequency of 31.25 KHz with a 4.0 MHz crystal. The
31.25 KHz reference frequency is used for both the UHF and
Sound PLLs.
The VHF divider is also a fixed ÷8.
the CHS pin voltage in order to select channel 3 or channel 4.
PIN SELECTION
By default (open condition), all pins are “HI”.
Table 2. Configuration Pin Settings
Pin No
The audio pre-emphasis circuit is a high-pass filter with an
The audio bandwidth specification is for 50 Hz to 15 KHz
The reference divider is a fixed ÷128 resulting in a refer-
The prescaler is a fixed ÷8 and is permanently engaged.
The programmable divider’s division ratio is controlled by
Pins CHS, PSS, and SFS are internally pulled up to 5.0 V.
16
1
2
9
Pin Name
PSave/
CHS
PSS
LOP
SFS
Power save Mode
LO (grounded)
(Low voltage)
LOP pin LO
5.5 MHz
14 dB
CH4
Application Specific Products
Freescale Semiconductor
HI (open or +5.0 V)
Normal Operation
(High impedance)
LOP pin HI
4.5 MHz
16 dB
CH3