MC34118DWR2 Freescale Semiconductor, MC34118DWR2 Datasheet - Page 8

• Manufacturer Part Number: MC34118DWR2
• Description: IC VOICE SWITCH SPKPHONE 28-SOIC
• Manufacturer: Freescale Semiconductor

Specifications of MC34118DWR2

• Function: Voice-Switched Speakerphone
• Number Of Circuits: 1
• Voltage - Supply: 3.5 V ~ 6.5 V
• Current - Supply: 5.5mA
• Operating Temperature: -20°C ~ 60°C
• Mounting Type: Surface Mount
• Package / Case: *
• Includes: Background Noise Monitor, Chip Disable, Dial Tone Detector, Driver Amplifiers, Level Detectors, Microphone Amplifier, MUTE
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power (watts): -
• Interface: -
• Other names: MC34118DWTR

speaker amplifier. On the transmit side, one level detector
(TLI2) is at the output of the microphone amplifier, while the
other (TLI1) is at the hybrid output. Outputs RLO1 and TLO1
feed a comparator, the output of which goes to the Attenuator
Control Block. Likewise, outputs RLO2 and TLO2 feed a
second comparator which also goes to the Attenuator Con-
trol Block. The truth table for the effects of the level detectors
on the Control Block is given in the section describing the
Control Block.
BACKGROUND NOISE MONITORS
guish speech (which consists of bursts) from background
noise (a relatively constant signal level). There are two back-
ground noise monitors — one for the receive path and one
for the transmit path. Referring to Figure 4, the receive back-
ground noise monitor is operated on by the RLI1--RLO1 level
detector, while the transmit background noise monitor is op-
erated on by the TLI2--TLO2 level detector. They monitor the
background noise by storing a dc voltage representative of
the respective noise levels in capacitors at CPR and CPT.
The voltages at these pins have slow rise times (determined
by the external RC), but fast decay times. If the signal at RLI1
(or TLI2) changes slowly, the voltage at CPR (or CPT) will
remain more positive than the voltage at the non--inverting
input of the monitor’s output comparator. When speech is
present, the voltage on the noninverting input of the com-
parator will rise quicker than the voltage at the inverting input
(due to the burst characteristic of speech), causing its output
to change. This output is sensed by the Attenuator Control
Block.
comparator from changing state unless the speech level ex-
ceeds the background noise by ≈4.0 dB. The time constant
MC34118
8
The purpose of the background noise monitors is to distin-
The 36 mV offset at the comparator’s input keeps the
SIGNAL
SIGNAL
INPUT
INPUT
5.1 k
5.1 k
0.1 µF
0.1 µF
(RLI2)
(TLI2)
RLI1
TLI1
V
V
B
B
--
+
--
+
350 Ω
350 Ω
(RLO2)
(TLO2)
2.0 µF
2.0 µF
RLO1
TLO1
LEVEL DETECTOR
LEVEL DETECTOR
Figure 4. Level Detectors
4.0
µA
4.0
µA
of the external RC (≈4.7 seconds) determines the response
time to background noise variations.
VOLUME CONTROL
voltage with respect to V
attenuators only in the receive mode. It has no effect in the
idle or transmit modes.
tor will be + 6.0 dB, and the gain of the transmit attenuator
will be -- 46 dB only when VLC is equal to V
duced below V
(see Figure 14), and the gain of the transmit attenuator is
increased such that their sum remains constant. Changing
the voltage at VLC changes the voltage at C
tenuator Control Block section), which in turn controls the
attenuators.
attenuator input signal at which noticeable distortion occurs.
and does not vary significantly with the VLC voltage or with
V
DIAL TONE DETECTOR
nected to the receive input (RXI) and the other input con-
nected to V
is in the receive mode, and the incoming signal is greater
than 15 mV (10 mVrms), the comparator’s output will
change, disabling the receive idle mode. The receive attenu-
ator will then be at a setting determined solely by the volume
control.
CC
The volume control input at VLC (Pin 13) is sensed as a
When in the receive mode, the gain of the receive attenua-
The volume control setting does not affect the maximum
The bias current at VLC is typically 60 nA out of the pin,
The dial tone detector is a comparator with one side con-
The purpose of this circuit is to prevent the dial tone
.
BACKGROUND
NOISE MONITOR
COMPARATOR
NOTE: External component values are
V
33 k
B
+
--
--
+
56 k
(C3)
B
applicaton dependent.
C4
with a 15 mV offset (see Figure 5). If the circuit
B
, the gain of the receive attenuator is reduced
(C1)
C2
--
+
36 mV
B
TO ATTENUATOR
CONTROL BLOCK
. The volume control affects the
--
+
(CPT)
CPR
B
. As VLC is re-
100 k
MOTOROLA
47 µF
T
(see the At-
V
CC