MC34118DW Freescale Semiconductor, MC34118DW Datasheet - Page 10

• Manufacturer Part Number: MC34118DW
• Description: IC VOICE SWITCH SPKPHONE 28-SOIC
• Manufacturer: Freescale Semiconductor

Specifications of MC34118DW

• 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: -

— To switch to idle quickly (fast idle), the current sources
— To switch to idle slowly (slow idle), the current sources
MICROPHONE AMPLIFIER
ing input internally connected to V
and the output are pinned out. Unlike most op--amps, the
amplifier has an all--NPN output stage, which maximizes
phase margin and gain--bandwidth. This feature ensures
stability at gains less than unity, as well as with a wide range
of reactive loads. The open loop gain is typically 80 dB
(f < 100 Hz), and the gain--bandwidth is typically 1.0 MHz
(See Figure 16). The maximum p--p output swing is typically
1.0 volt less than V
until current limiting is reached (typically 1.5 mA). Input bias
current at MCI is typically 40 nA out of the pin.
the gain of the amplifier to ≈-- 39 dB (with RMI = 5.1 kΩ) by
MC34118
10
The microphone amplifier (Pins 10, 11) has the noninvert-
The muting function (Pin 12), when activated, will reduce
R
MUTE
are turned off, and the internal 2.0 kΩ resistor is switched
in, discharging the capacitor to V
= 2.0 k x C
are turned off, the switch at the 2.0 kΩ resistor is open,
and the capacitor discharges to V
resistor R
C
T
CT
V
T
B
Figure 6. CT Attenuator Control Block Circuit
FROM
Figure 7. Microphone Amplifier and Mute
MIKE
I
1
T
T
2.0 k
V
with a time constant = R
.
CC
R
60 µA
EACH
MI
I
2
CC
75 k
MCI
with an output impedance of < 10 Ω
75 k
V
B
CONTROL
CIRCUIT
R
+
--
MF
B
+
--
, while the inverting input
V
B
B
CC
T
with a time constant
through the external
x C
4
MCO
GAIN = –
TO
ATTENUATORS
T
C1 -- C4
VOL. CONTROL
DIAL TONE DET.
AGC
.
R
R
MF
MI
shorting the output to the inverting input (see Figure 7). The
mute input has a threshold of ≈1.5 volts, and the voltage at
this pin must be kept within the range of ground and V
(see Figure 17). If the mute function is not used, the pin
should be grounded.
HYBRID AMPLIFIERS
conjunction with an external transformer, provide the two--to--
four wire converter for interfacing to the telephone line. The
gain of the first amplifier (HTI to HTO--) is set by external re-
sistors (gain = -- R
the second amplifier, the gain of which is internally set at
-- 1.0. Unlike most op--amps, the amplifiers have an all--NPN
output stage, which maximizes phase margin and gain--
bandwidth. This feature ensures stability at gains less than
unity, as well as with a wide range of reactive loads. The
open loop gain of the first amplifier is typically 80 dB, and the
gain bandwidth of each amplifier is ≈1.0 MHz (see Fig-
ure 16). The maximum p--p output swing of each amplifier is
typically 1.2 volts less than V
< 10 Ω until current limiting is reached (typically 8.0 mA). The
output current capability is guaranteed to be a minimum of
5.0 mA. The bias current at HTI is typically 30 nA out of the
pin.
the Block Diagram (Figure 2). The block labeled ZBal is the
balancing network necessary to match the line impedance.
FILTER
nal components. The circuit within the MC34118, from pins FI
to FO is a buffer with a high input impedance (> 1.0 MΩ), and
a low output impedance (< 50 Ω). The configuration of the
external components determines whether the circuit is a
high--pass filter (as shown in Figure 2), a low--pass filter, or a
band--pass filter.
ure 8, the filter will keep out 60 Hz (and 120 Hz) hum which
can be picked up by the external telephone lines. As a low
pass filter (Figure 9), it can be used to roll off the high end
frequencies in the receive circuit, which aids in protecting
against acoustic feedback problems.
-- 3.0
-- 30
The two hybrid amplifiers (at HTO+, HTO--, and HTI), in
The connections to the coupling transformer are shown in
The operation of the filter circuit is determined by the exter-
As a high pass filter, with the components shown in Fig-
0
f
FOR C1 = C2
N
50
= 1
305 Hz
2π
f
N

C 2 R1R2
Figure 8. High Pass Filter
1
HF
/R
HI
4700 pF
in Figure 2), and its output drives
56 k
R1
C1
CC
4700 pF
with an output impedance of
C2
V
B
FI
MC34118
260 µA
MOTOROLA
100 k
V
CC
FO
CC