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MC33111D 参数 Datasheet PDF下载

MC33111D图片预览
型号: MC33111D
PDF下载: 下载PDF文件 查看货源
内容描述: 低压压扩硅单片集成电路 [Low Voltage Compander Silicon Monolithic Integrated Circuit]
分类和应用:
文件页数/大小: 12 页 / 1080 K
品牌: LANSDALE [ LANSDALE SEMICONDUCTOR INC. ]
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ML33111  
LANSDALE Semiconductor, Inc.  
Legacy Applications Information  
The ML33111 compander is not limited to RF or long dis-  
tance telephony applications. It can be used in any system  
requiring either an improved signal-to-noise ratio, or a  
reduced dynamic range. Such applications include tele-  
phones, speakerphones, tape recorders, wireless microphones,  
digital recording, and many others.  
quency filtering, should be used and dedicated to the analog  
portion of the circuit. The ripple content of the supply should  
not allow its magnitude to exceed the values in the  
Recommended Operating Conditions table.  
The PC board tracks supplying V  
and ground to the  
CC  
ML33111 should preferably not be at the tail end of the bus  
distribution, after passing through a maze of digital circuitry.  
The analog circuitry containing the ML33111 should be close  
to the power supply, or the connector where the supply volt-  
Power Supplies, Grounding  
The PC board layout, and the quality of the power supplies  
and the ground system at the IC are very important in order  
to obtain proper operation. Noise, from any source, coming  
ages enter the board. If V  
to other parts of the board, then it is preferable to have dedi-  
cated lines directly to the ML33111 and associated circuitry.  
is supplying considerable current  
CC  
into the device on V  
put, or incorrect gain levels.  
or ground, can cause a distorted out-  
CC  
V
must be decoupled to the appropriate ground at the  
PC Board Layout  
Although this device is intended for use in the audio fre-  
quency range, the various amplifiers have a bandwidth of  
CC  
IC (within 1” max.) with a 4.7 µF capacitor and a 0.01 µF  
ceramic. A tantalum capacitor is recommended for the larger  
value if very high frequency noise is present, since electrolyt- 300 kHz, and can therefore oscillate at frequencies outside  
ic capacitors simply have too much inductance at those fre-  
quencies. The quality of the power supply voltage should be  
checked at the IC with a high frequency scope. Noise spikes  
(always present if digital circuits are near this IC) can easily  
exceed 400 mV, and if they get into the IC, the output can  
have noise or distortion. Noise can be reduced by inserting  
resistors and/or inductors between the supply and the IC.  
If switching power supplies are used, there will be spikes  
of 0.5 V or greater at frequencies of 50 kHz – 1.0 MHz.  
These spikes are generally more difficult to reduce because  
the voiceband should there be excessive stray capacitance or  
other unintended feedback loops. A solid ground plane is  
strongly recommended to minimize coupling of any digital  
noise into the analog section. Use of wire wrapped boards  
should definitely be avoided.  
Since many applications of the ML33111 compander  
involve voice transmission over RF links, care must be taken  
in the design of the product to keep RF signals out of the  
ML33111 and associated circuitry. This involves proper lay-  
out of the PC boards and the physical arrangement of the  
of their greater energy content. In extreme cases, a 3-terminal boards, shielding, proper RF ground, etc.  
regulator (e.g., MC78L05ACP), with appropriate high fre-  
DEFINITIONS  
Attack Time — The settling time for a circuit after its input signal  
has been increased.  
dBrnC— Indicates a dBrn measurement using a C-message  
weighting filter.  
Attenuation — A decrease in magnitude of a communication sig-  
nal, usually expressed in dB.  
Decay Time— The settling time for a circuit after its input signal  
has been decreased.  
Bandwidth — The range of information carrying frequencies of a  
communication system.  
Expander— A circuit which expands, or increases the dynamic  
range of a signal by amplifying strong signals and attenuating low  
level signals.  
Gain— The change in signal amplitude (increase or decrease) after  
passing through an amplifier, or other circuit stage. Usually  
expressed in dB, an increase is a positive number, and a decrease is a  
negative number.  
Mute— Reducing the level of an audio signal, generally so that it  
is inaudible. Partial muting is used in some applications.  
Passthrough— Bypassing the compression and/or expansion func-  
tion by setting the gain to a fixed value (usually unity). This is usual-  
ly employed when data, rather than voice, is to be transmitted with-  
out attenuation.  
Power Supply Rejection Ratio— The ability of a circuit to reject  
outputting noise, or ripple, which is present on the power supply  
lines. PSRR is usually expressed in dB.  
Channel Separation — The ability of one circuit to reject out-  
putting signals which are being processed by another circuit. Also  
referred to as crosstalk rejection, it is usually expressed in dB.  
Compander — A contraction of the words compressor and  
expander. A compander is composed of two circuits, one of each  
kind.  
Compressor — A circuit which compresses, or reduces, the  
dynamic range of a signal by attenuating strong signals and amplify-  
ing low level signals.  
dB — A power or voltage measurement unit, referred to another  
power or voltage. It is generally computed as:  
10 x log (P1/P2) for power signals, and  
20 x log (V1/V2) for voltage signals.  
dBm — An indication of signal power. 1.0 mW across 600 , or  
0.775 Vrms, is typically defined as 0 dBm for telecom applications.  
Any voltage level is converted to dBm by:  
Signal to Noise Ratio— The ratio of the desired signal to unwant-  
ed signals (noise) within a defined frequency range. The larger the  
number, the better.  
dBm = 20 x log (Vrms/0.775), or  
dBm = [20 x log (Vrms)] + 2.22.  
Voiceband— That portion of the audio frequency range used for  
transmission in the telephone system. Typically it is 300-3400 Hz.  
Zero dB Point— The signal level which has its amplitude  
unchanged by a compressor or expander.  
dBrn — Indicates a dBm measurement relative to 1.0 pW power  
level into 600 . Generally used for noise measurements, 0 dBm =  
–90 dBm.  
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