mc33111d Freescale Semiconductor, Inc, mc33111d Datasheet - Page 10

• Manufacturer Part Number: mc33111d
• Description: Low Voltage Compander
• Manufacturer: Freescale Semiconductor, Inc

Power Supply
and 7.0 V, and a nominal current of
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
MC33111 compander. The following points apply:
a) The values shown adjacent to some components are
b) The values for the unlabeled components are application
Signal-To-Noise Improvement
compander type circuits was to improve the signal-to-noise
ratio of long distance communications circuits, and of voice
circuits which are transmitted 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 level. At the receiving end, the signal is
MOTOROLA
10
Microphone
The MC33111 requires a supply voltage between 3.0 V
Figure 18 indicates a typical implementation of the
Among the basic reasons for the original development of
based on the expected use of the IC:
— The input capacitors (Pins 3 and 14) provide a 3.0 dB
— The rectifier capacitors provide attack and decay times
dependent:
— The components around the op amps depend on their
— The value of the capacitors at the compressor and
rolloff of
voiceband.
as indicated in the Electrical Tables.
use.
Expander
Input
Compressor
Input
V+
30 Hz, a decade below the nominal
1.0 µF
1.0 µF
0.47
0.47
14
10
11
3
5
9
MC33111
Vb
1.6 mA. The supply
10 k
APPLICATION INFORMATION
Rectifier
Figure 18. Typical Application
∆ Gain
Vb
7
40 k
Vb
15 k
7.5 k
40 k
Rectifier
6
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.
c) If either the compressor or expander is not used, its input
d) The two op amps can be used for any purpose which suits
e) If an op amp is not used, its output and input must be
f) The logic inputs (Pins 4, 8, 12) are TTL/CMOS compatible.
∆ Gain
then expanded back to is 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
transmitter and receiver. The MC33111 was designed for a
two-to-one compression and expansion, i.e. a 60 dB dynamic
signal is compressed 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
must not be left open. It can be connected to ground
either through a capacitor, or directly to ground.
the application. The indicated use of the one op amp as a
microphone amplifier is only an example.
connected together. Do not leave Pin 7 or Pin 9 open.
The logic high voltage must not exceed the V CC voltage on
the MC33111. Any unused input should be connected to
ground and not left open.
expander outputs depend on the circuit to which they
are connected.
Passthrough
Vb
Reference
Mute/
Generator
Logic
Bias &
20 k
(See Text For Component Values)
15
2
16
1
4
12
8
CM
EM
PT
4.7/
0.01
Other Control Circuit
Expander
Output
Compressor
Output
µP or
V CC
MC33111