Freescale Semiconductor, Inc.Modulator Functionality
The audio pre-emphasis circuit is a high-pass filter with an external capacitor C1 and an internal resistor
(100kOhms typical). The recommended capacitor value (750pF) is for M/N standards; time constant is
75µs. It is 470pF for B/G standards (50µs).
Audio bandwidth specification is for 50Hz to 15Khz range, with pre-emphasis circuit engaged. Without
this pre-emphasis circuit, it is possible to extend the audio bandwidth to the high frequencies as there is no
internal frequency limitation (stereo application).
12.8 PLL Section — Dividers
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 VHF divider is different for each of
the 3 versions.
The programmable divider’s division ratio is controlled by CHS pin voltage in order to get the following
VHF frequencies:
Device
Channel
VHF divider
CH3 = 61.25Mhz
CH4 = 67.25Mhz
CH1 = 91.25Mhz
CH2 = 97.25Mhz
MC44BC375U
8
MC44BC375J
MC44BC375T
6
3
CH13 = 211.25Mhz
12.9 Selectable Pins
Pins CHS, PSS, SFS are internally pulled up to 5V.
MOTOROLA
MC44BC375/U/J/T Technical Data
13
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MOTOROLA [ MOTOROLA ]
