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| 型号： | MC44BS373CAFCEVK |
| 厂商： | Freescale Semiconductor |
| 文件页数： | 18/52页 |
| 文件大小： | 0K |
| 描述： | KIT EVAL FOR BS373CAFC 16PIN |
| 标准包装： | 1 |
| 主要目的： | 音频视频集成调制器 |
| 已用 IC / 零件： | MC44BS373CA |
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MC44BS373CA Data Sheet
MC44BS373CA Modes of Operation
15.11 Sound Section
The oscillator is fully integrated and does not require any external components. An internal low-pass filter
and matched structure provide very low harmonics levels.
The sound modulator system consists of an FM modulator incorporating the sound subcarrier oscillator. The
audio input signal is AC-coupled into the amplifier, which then drives the modulator. For mono applications,
the audio pre-emphasis circuit is a high-pass filter with an external capacitor and an internal resistor
(106 K
typical).
The recommended capacitor value for BG standard (with a time constant of 50
S) is 470 pF.
The recommended capacitor value for M/N standard (with a time constant of 75
S) is 750 pF.
The sound reference divider is a programmable divide-by-128 or divide-by-64, resulting in a reference
frequency of 31.25 kHz or 62.5 kHz with a 4.0-MHz crystal.
This reference frequency can be selected by bus (bit SREF), depending on the application. For instance,
when the audio bandwidth is required to be extended (for stereo application), it is possible to select the
higher value (62.5 kHz) to avoid any interference between the reference and the audio signals.
For stereo applications, the audio signal is already encoded in the baseband stereo encoder. It is not
necessary to use a pre-emphasis, and in this case the pre-emphasis capacitor must be removed.
Sometimes for the same application it is useful to increase the FM deviation. To increase FM deviation,
replace the original pre-emphasis capacitor with a fixed 100-nF capacitor. Adding this value boosts the
deviation and does not create a pre-emphasis.
Without pre-emphasis, the audio bandwidth extends to 60 kHz.
To increase the audio bandwidth at low frequencies it is recommended to change the sound PLL loop filter.
It is also recommended to increase the values of the loop filter capacitors. The recommended values are 1
F
and 100 nF.
It is possible to create a peak for the low frequencies (from 30 to 80 Hz) by adjusting the resistor of the sound
loop filter. A flat response is given with a value of 5.6 K
but this value can be set to 4.7 K. This gives a
peak of about 1 dB at 40 Hz and extends the low-frequency cut-off to 28 Hz.
The following figure plots the resulting bandwidth for low frequencies and for the whole bandwidth (up to
60 kHz).
The first chart represents the audio bandwidth for low frequencies (20 to 150 Hz) for two sets of sound loop
filters. The first set with 1
F + 100 nF + 5.6 K gives a flat response. The second set with 1 F + 100 nF
+ 4.7 K
gives a peak of about 1 dB at 60 Hz. It is possible to adjust this peak by changing the resistor value.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MC44BS373CAFCR2 | 功能描述:IC MODULATOR AUD/VID U/V 20-QFN RoHS:是 类别:集成电路 (IC) >> 专用 IC 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:1 系列:- 类型:调帧器 应用:数据传输 安装类型:表面贴装 封装/外壳:400-BBGA 供应商设备封装:400-PBGA（27x27） 包装:散装 |
| MC44BS373CAR2 | 制造商:MOTOROLA 制造商全称:Motorola, Inc 功能描述:PLL-Tuned UHF and VHF Audio/Video High-Integration Modulator |
| MC44BS373CR2 | 制造商:MOTOROLA 制造商全称:Motorola, Inc 功能描述:PLL-Tuned UHF and VHF Audio/Video High-Integration Modulator |
| MC44BS374 | 制造商:FREESCALE 制造商全称:Freescale Semiconductor, Inc 功能描述:MC44BS374 |
| MC44BS374CA | 制造商:FREESCALE 制造商全称:Freescale Semiconductor, Inc 功能描述:SO16NB Package |
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