mc44bc373c Freescale Semiconductor, Inc, mc44bc373c Datasheet - Page 20

• Manufacturer Part Number: mc44bc373c
• Description: Pll Tuned Uhf And Vhf Audio/video High Integration Modulator
• Manufacturer: Freescale Semiconductor, Inc

Modulator Description
13.11 Sound Section
The multivibrator oscillator is fully integrated and does not require any external components. An internal
low-pass filter and matched structure give a very low harmonics level.
The sound modulator system consists of the following two types:
The audio input signal is AC-coupled into the amplifier, which then drives both types of modulator.
The audio pre-emphasis circuit is a high-pass filter with an external capacitor and an internal resistor
(100kOhms). The recommended capacitor value (470pF) is for BG standard; time constant is 50µS.
13.12 Test Pattern Generator
The IIC generates a simple test pattern, which can be switched under bus control to permit a TV receiver to
easily tune to the modulator output. The pattern consists of two white vertical bars on a black background
and a 976Hz audio test signal.
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An FM modulator incorporating the sound subcarrier oscillator
An AM modulator (MC44BC373C only)
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MC44BC373C/374C Technical Data
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Table 1. Test Pattern Generator
Go to: www.freescale.com
20
24 28
30
TIME IN µS.
40
44
7/10
50
3/10
60
64