mc33111p Lansdale Semiconductor, Inc., mc33111p Datasheet - Page 11

• Manufacturer Part Number: mc33111p
• Description: Low Voltage Compander
• Manufacturer: Lansdale Semiconductor, Inc.

ML33111
Legacy Applications Information
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.
Power Supplies, Grounding
and the ground system at the IC are very important in order
to obtain proper operation. Noise, from any source, coming
into the device on V CC or ground, can cause a distorted out-
put, or incorrect gain levels.
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-
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.
of 0.5 V or greater at frequencies of 50 kHz – 1.0 MHz.
These spikes are generally more difficult to reduce because
of their greater energy content. In extreme cases, a 3-terminal
regulator (e.g., MC78L05ACP), with appropriate high fre-
has been increased.
nal, usually expressed in dB.
communication system.
putting signals which are being processed by another circuit. Also
referred to as crosstalk rejection, it is usually expressed in dB.
expander. A compander is composed of two circuits, one of each
kind.
dynamic range of a signal by attenuating strong signals and amplify-
ing low level signals.
power or voltage. It is generally computed as:
0.775 Vrms, is typically defined as 0 dBm for telecom applications.
Any voltage level is converted to dBm by:
level into 600 Ω. Generally used for noise measurements, 0 dBm =
–90 dBm.
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The ML33111 compander is not limited to RF or long dis-
The PC board layout, and the quality of the power supplies
V CC must be decoupled to the appropriate ground at the
If switching power supplies are used, there will be spikes
Attack Time — The settling time for a circuit after its input signal
Attenuation — A decrease in magnitude of a communication sig-
Bandwidth — The range of information carrying frequencies of a
Channel Separation — The ability of one circuit to reject out-
Compander — A contraction of the words compressor and
Compressor — A circuit which compresses, or reduces, the
dB — A power or voltage measurement unit, referred to another
dBm — An indication of signal power. 1.0 mW across 600 Ω, or
dBrn — Indicates a dBm measurement relative to 1.0 pW power
10 x log (P1/P2) for power signals, and
20 x log (V1/V2) for voltage signals.
dBm = 20 x log (Vrms/0.775), or
dBm = [20 x log (Vrms)] + 2.22.
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DEFINITIONS
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.
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-
ages enter the board. If V CC is supplying considerable current
to other parts of the board, then it is preferable to have dedi-
cated lines directly to the ML33111 and associated circuitry.
PC Board Layout
quency range, the various amplifiers have a bandwidth of
≈300 kHz, and can therefore oscillate at frequencies outside
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.
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
boards, shielding, proper RF ground, etc.
weighting filter.
has been decreased.
range of a signal by amplifying strong signals and attenuating low
level signals.
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.
is inaudible. Partial muting is used in some applications.
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.
outputting noise, or ripple, which is present on the power supply
lines. PSRR is usually expressed in dB.
ed signals (noise) within a defined frequency range. The larger the
number, the better.
transmission in the telephone system. Typically it is 300-3400 Hz.
unchanged by a compressor or expander.
The PC board tracks supplying V CC and ground to the
Although this device is intended for use in the audio fre-
Since many applications of the ML33111 compander
dBrnC— Indicates a dBrn measurement using a C-message
Decay Time— The settling time for a circuit after its input signal
Expander— A circuit which expands, or increases the dynamic
Gain— The change in signal amplitude (increase or decrease) after
Mute— Reducing the level of an audio signal, generally so that it
Passthrough— Bypassing the compression and/or expansion func-
Power Supply Rejection Ratio— The ability of a circuit to reject
Signal to Noise Ratio— The ratio of the desired signal to unwant-
Voiceband— That portion of the audio frequency range used for
Zero dB Point— The signal level which has its amplitude
LANSDALE Semiconductor, Inc.
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