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PDF IL34118 Data sheet ( Hoja de datos )
| Número de pieza | IL34118 | |
| Descripción | Voice Switched Speakerphone Circuit | |
| Fabricantes | IK Semiconductor | |
| Logotipo |  |
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TECHNICAL DATA
Voice Switched Speakerphone Circuit
IL34118
The IL34118 Voice Switched Speakerphone Circuit incorporates the
necessary amplifiers, attenuators, level detectors, and control algorithm to
form the heart of a high quality hands-free speakerphone system. Included
are a microphone amplifier with adjustable gain and MUTE control,
Transmit and Receive attenuators which operate in a complementary
manner, level detectors at both input and output of both attenuators, and
background noise monitors for both the transmit and receive channels. A
Dial Tone Detector prevents the dial tone from being attenuated by the
Receive background noise monitor circuit. Also included are two line
driver amplifiers which can be used to form a hybrid network in
conjunction with an external coupling transformer. A high pass filter can
be used to filter out 60 Hz noise in the receive channel, or for other
filtering functions. A Chip Disable pin permits powering down the entire
circuit to conserve power on long loops where loop current is at a
minimum.
The IL34118 may be operated from a power supply, or it can be powered
from the telephone line, requiring typically 5.0 mA. The IL34118 can be
interfaced directly to Tip and Ring (through a coupling transformer) for
stand-alone operation, or it can be used in conjunction with a handset
speech network and or other features of a feature phone.
ORDERING INFORMATION
IL34118N Plastic
IL34118DW SOIC
TA = -25° to 70° C for all packages
• Improved Attenuator Gain Range: 52 dB Between Transmit and
www.DataSheet4U.comReceive
• Low Voltage Operation for Line-Powered Applications (3.0-6.5 V)
• 4 Point Signal Sensing for Improved Sensitivity
PIN ASSIGNMENT
• Background Noise Monitors for Both Transmit and Receive Paths
• Microphone Amplifier Gain Set by External Resistors - Mute
Function Included
• Chip Disable for Active Standby Operation
• On Board Filter Pinned-Out for User Defined Function
• Dial Tone Detector to Inhibit Receive Idle Mode During Dial Tone
Presence
1
1 page  
IL34118
ATTENUATOR CONTROL BLOCK
The Attenuator Control Block has the seven inputs
described above:
- The output of the comparator operated by RLO2 and
TLO2 (microphone/speaker side) - designated C1.
- The output of the comparator operated by RLO1 and
TLO1 (Tip/Ring) side) - designated C2.
- The output of the transmit background noise
monitor - designated C3.
- The output of the receive background noise
monitor - designated C4.
- The volume control.
- The dial tone detector.
- The AGC circuit.
The single output of the Control Block controls the
two attenuators. The effect of C1-C4 is as follows:
Inputs
Output
C1 C2 C3 C4
Mode
Tx Tx 1 X Transmit
Tx Rx Y
Y Fast Idle
Rx Tx
Y
Y Fast Idle
Rx Rx
X
1
Receive
Tx Tx 0 X Slow Idle
Tx Rx
0
0 Slow Idle
Rx Tx
0
0 Slow Idle
Rx Rx
X
0 Slow Idle
X = Don’t Care; Y = C3 and C4 are not both 0
A definition of the above terms:
1) “Transmit” means the transmit attenuator is fully
on (+6.0 dB), and the receive attenuator is at max.
attenuation (-46 dB).
2) “Receive” means both attenuators are controlled by
the volume control. At max. volume, the receive
attenuator is fully on (6.0 dB), and the transmit
attenuator is at max. attenuation (-46 dB).
3) “Fast Idle” means both transmit and receive speech
are present in approximately equal levels. The
attenuators are quickly switched (30 ms) to idle
until one speech level dominates the other.
4) “Slow Idle” means speech has ceased in both
transmit and receive path. The attenuators are then
slowly switched (1 second) to the idle mode.
5) Switching to the full transmit or receive modes
from any other mode is at the fast rate (30 ms).
A summary of the truth table is as follows:
1) The circuit will switch to transmit if: a) both
transmit level detectors sense higher signal levels
relative to the respective receive level detectors (TLI1
versus RLI1, TLI2 versus RLI2), and b) the transmit
background noise monitor indicates the presence of
speech.
2) The circuit will switch to receive if: a) both receive
level detectors sense higher signal levels relative to the
respective transmit level detectors, and b) the receive
background noise monitor indicates the presence of
speech.
3) The circuit will switch to the fast idle mode if the
level detectors disagree on the relative strengths of the
signal levels, and at least one of the background noise
monitors indicates speech. For example, referring to the
Expanded Logic Diagram (Figure 8), if there is
sufficient signal at the microphone amp output (TLI2) to
override the speaker signal (RLI2), and there is
sufficient signal at the receive input (RLI1) to override
the signal at the hybrid output (TLI1), and either or both
background monitors indicate speech, then the circuit
will be in the fast idle mode. Two conditions which can
cause the fast idle mode to occur are a) when both
talkers are attempting to gain control of the system by
talking at the same time, and b) when one talker is in a
very noisy environment, forcing the other talker to
continually override that noise level. In general, the fast
idle mode will occur infrequently.
4) The circuit will switch to the slow idle mode when
a) both talkers are quiet (no speech present), or b) when
one talker’s speech level is continuously overriden by
noise at the other speaker’s location.
The time required to switch the circuit between
transmit, receive, fast idle and slow idle is determined in
part by the components at the CT pin (Pin 14). A
schematic of the CT circuitry is shown in Figure 4 and
operates as follows:
- RT is typically 120 kΩ, and CT typically 5.0 µF.
- To switch to the receive mode, I1 is turned on (I2 is
off), charging the external capacitor to +240 mV
above VB. (An internal clamp prevents further
charging of the capacitor.)
- To switch to the transmit mode, I2 is turned on (I1 is
off) bringing down the voltage on the capacitor to -
240 mV with respect to VB.
- To switch to idle quickly (fast idle), the current
sources are turned off, and the internal 2.0 kΩ
resistor is switched in, discharging the capacitor to
VB with a time constant = 2.0 KΩ x CT.
- To switch to idle slowly (slow idle), the current
sources are turned off, the switch at the 2.0 kΩ
resistor is open, and the capacitor discharges to VB
through the external resistor RT with a time constant
= RT x CT.
5
5 Page 
IL34118
ELECTRICAL CHARACTERISTICS (TA = -25 to +70°C, VCC = 5.0 V , CD = 0.8 V, unless noted)
Symbol
Parameter
Test Conditions
HYBRID AMPLIFIERS
HVOS HTO - Offset
VHTO- - VB,
Feedback R= 51 KΩ
HBVOS HTO - to HTO+ Offset
Feedback R= 51 KΩ
AVOLH Open Loop Gain
AVCLH
VHT-H
VHT-L
VHT+H
VHT+L
Closed Loop Gain
HTO- High Voltage
HTO- Low Voltage
HTO+ High Voltage
HTO+ Low Voltage
HTI to HTO-, f = 100 Hz,
VHTI = 20 mV
HTO- to HTO+
IOUT=-5.0 mA, VHTI=VB -1.0 V
IOUT=5.0 mA, VHTI=VB +1.5 V
IOUT=-5.0 mA,VHTI=VB +1.5 V
IOUT=5.0 mA, VHTI=VB -1.0 V
LEVEL DETECTORS AND BACKGROUND NOISE MONITORS
ITH* Transmit-Receive Switching Ratio of Current at RLI1 + RLI2
Threshold
to 20 µA at TLI1 + TLI2 to
switch from Tx to Rx
FILTER
FOVOS Voltage Offset at FO
VFO -VB, 220 KΩ from VB to FI
IFO FO Sink Current
VB = VFO, VFI = 0 V
Guaranteed
Limits
Min Max
VB - 25 VB +25
VB - 37 VB +37
57 -
-2.8 2.2
2.8 -
- 375
2.8 -
- 562
0.8 1.2
VB- VB +25
250
112 500
Unit
mV
mV
dB
dB
V
mV
V
mV
mV
µA
Note. 1. All currents into a device pin are positive, those out of a pin are negative. Algebraic convention rather than
magnitude is used to define limits.
* @25°C
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet IL34118.PDF ] | |
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