mc33111p Lansdale Semiconductor, Inc., mc33111p Datasheet - Page 10

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

ML33111
Power Supply
and a nominal current of ≈ 1.6 mA. The supply voltage should be
well filtered and free of ripple. A minimum of 4.7 µF in parallel with
a 0.01 µF capacitor is recommended for filtering and RF bypass.
Typical Application Circuit
compander. The following points apply:
Signal-To-Noise Improvement
der type circuits was to improve the signal-to-noise ratio of long dis-
tance communications circuits, and of voice circuits which are trans-
mitted over RF links (CBs, walkie-talkies, cordless phones, etc.).
Since much of the interfering noise heard at the receiving end of a
transmission is due to noise picked up, for example, in the airway
portion of the RF link, the compressor was developed to increase the
low-level signals at the transmitting end. Then any noise picked up in
the RF link would be a smaller percentage of the transmitted signal
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The ML33111 requires a supply voltage between 3.0 V and 7.0 V ,
Figure 18 indicates a typical implementation of the ML33111
a) The values shown adjacent to some components are based on
b) The values for the unlabeled components are application dependent:
Among the basic reasons for the original development of compan-
the expected use of the IC:
—The input capacitors (Pins 3 and 14) provide a 3.0 dB rolloff
— The rectifier capacitors provide attack and decay times as
— The components around the op amps depend on their use.
— The value of the capacitors at the compressor and expander
of ≈ 30 Hz, a decade below the nominal voiceband.
indicated in the Electrical Tables.
outputs depend on the circuit to which they are connected.
Microphone
Expander
Input
Compressor
Input
V+
1.0 µF
1.0 µF
0.47
0.47
LEGACY APPLICATIONS INFORMATION
14
10
11
3
5
9
ML33111
Vb
10 k
Rectifier
Figure 18. Typical Application
∆ Gain
Vb
7
www.lansdale.com
40 k
Vb
15 k
7.5 k
40 k
Rectifier
is used internally as an AC ground. It is not available directly
at any pins, but can be obtained as a buffered reference from
either op amp by connecting the op amp as a follower.
level. At the receiving end, the signal is then expanded back to its
original level, retaining the same high signal-to-noise ratio. While the
above explanation indicates it is not necessary to attenuate strong
signals (at the transmitting end), a benefit of doing this is the
reduced dynamic range which must be handled by the system trans-
mitter and receiver. The ML33111 was designed for a two-to-one
compression and expansion, i.e. a 60 dB dynamic signal is com-
pressed to a 30 dB dynamic range, transmitted to the receiving end,
and then expanded back to a 60 dB dynamic range.
Vb is an internally generated reference set at ≈ +1.5 V, and
c) If either the compressor or expander is not used, its input must
d) The two op amps can be used for any purpose which suits the
e) If an op amp is not used, its output and input must be connected
f) The logic inputs (Pins 4, 8, 12) are TTL/CMOS compatible. The
6
∆ Gain
not be left open. It can be connected to ground either through a
capacitor, or directly to ground.
application. The indicated use of the one op amp as a micro
phone amplifier is only an example.
together. Do not leave Pin 7 or Pin 9 open.
logic high voltage must not exceed the V CC voltage on the
ML33111. Any unused input should be connected to ground
and not left open.
Passthrough
Vb
Reference
Mute/
Generator
Logic
Bias &
20 k
(See Text For Component Values)
15
2
16
1
4
12
8
CM
EM
PT
LANSDALE Semiconductor, Inc.
4.7/
0.01
Other Control Circuit
Expander
Output
Compressor
Output
µP or
V CC
Issue A