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KL34018 Schematic ( PDF Datasheet ) - IK Semiconductor

Teilenummer KL34018
Beschreibung LINEAR INTEGRATED CIRCUIT
Hersteller IK Semiconductor
Logo IK Semiconductor Logo 




Gesamt 14 Seiten
KL34018 Datasheet, Funktion
TECHNICAL DATA
LINEAR INTEGRATED CIRCUIT
VOICE SWITCHED SPEAKER PHONE CIRCUIT
KL34018
DESCRIPTION
The KL34018 speaker-phone integrated circuit incorporates the necessary
functions to produce a high quality hands-free speaker-phone system.
The applications include household and office speaker-phones,
intercom systems, hand free kit for mobile phones, and others
FEATURES
All necessary level detection and attenuation controls for a hand-free
telephone included.
Background noise level monitoring with long time constant.
Background sound level compensation for transmit and
receive levels as well as the background level.
Wide operating dynamic range through signal compression.
On-chip voltage regulators illuminate external regulators for
lining operation.
Power audio amplifier for typical 100mW output (into 25
ohms)with peak limiting for speaker to minimize distortion.
Chip Select pin for active/stand by operation.
Volume control function for external volume control.
Standard 28-pin plastic DIP and SOP package.
ORDERING INFORMATION
Device
Operating
Temperature Range
KL34018N
KL34018D
KL34018DT
TA = -25to 85C
KL34018N Plastic
KL34018D/DW SOIC
Package
DIP28
SOP28
SOP28
Packing
Tube
Tube
Tape & Reel
ABSOLUTE MAXIMUM RATINGS (Ta=25,Voltages referred to pin 22)
PARAMETER
VALUE
UNIT
V+ terminal Voltage (pin 16)
-1.0 to +12
V
CS (pin 18)
-1.0 to +12
V
Speaker amplifier Ground(pin 14)
-1.0 to +3.0
V
VLC(pin 24)
-1.0 to +Vcc
V
Storage temperature
-65 to +150
* Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device.
These are stress ratings only and functional operation of the device at these or any other conditions beyond those
indicated under “recommended operating conditions” is not implied.
Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
RECOMMENDED OPERATION CONDITIONS
PARAMETER
V+ Terminal Voltage (pin 16)
CS (pin 18)
Vcc (pin 20)
VLC(pin 24)
Receive Signal(pin 27)
Microphone Signal(pin 9)
Speaker Amplifier Ground (pin 14)
Ambient Temperature
VALUE
+6.0 to +11
0 to +11
0 to 3.0
0.55VB to VB
0 to 250
0 to 5.0
-10 to +10
-25 to +85
UNIT
V
V
mA
V
mVrms
mVrms
mVdc
2011, March, Rev. 01






KL34018 Datasheet, Funktion
KL34018
FUNCTION DECRIPTION
ATTENUATORS
The transmit and receive attenuators are
complementary in function, i.e., when one is at
maximum gain the other is at maximum attenuation, and
vice versa. They are never both on or both off. Their
main purpose is to control the transmit and receive paths
to provide the half-duplex operation required of a
speakerphone. The attenuators are controlled solely by
the voltage at the ACF pin (Pin 25). The ACF voltage is
provided by the Attenuator Control block, which
receives 3 inputs: a) the Rx-Tx Comparator, b) the
Transmit Detector Comparator, and c) the Volume
Control. The response of the attenuators is based on the
difference of the ACF voltage from VCC, and therefore
a simple method for monitoring the circuit operation is
to monitor this voltage difference (referred to as AVacf).
If AVacf is approximately 6 millivolts the transmit
attenuator is fully on and the receive attenuator is fully
off (transmit mode). If AVacf is approximately 150
millivolts the circuit is in the re- ceive mode. If AVacf is
approximately 75 millivolts, the circuit is in the idle
mode, and the two attenuators are at gain settings
approximately half way (in dB) between their fully on
and fully off positions.
The maximum gain and attenuation values are
determined by the three resistors RR, RTX, and RRX
(Refer to Figures 2, 3 and 4). RR affects both attenuators
ac- cording to its value RELATIVE to RTX and RRX,
which is why Figure 4 indicates the variations versus the
ratio of the other resistors to RR. (GRX and GTX are the
maximum gains, and ARX and ATX are the maximum
attenuations). RTX affects the gain and attenuation of
only the transmit attenuator according to the curves of
Figure 2, while RRX affects only the receive attenuator
according to Figure 3. As can be seen from the figures,
the gain difference (from on to off) is a reasonably
constant 45 dB until the upper gain limit is approached.
A value of 30 k is recommended for RR as a starting
point, and then RTX and RRX selected to suit the
particular design goals.
The input impedance of the attenuators (at TXI and
RXI) is typically 5.0 kR, and the maximum input signal
which will not cause output distortion is 250 mVrms
(707 mVp-p). The 4300 ohm resistor and 0.01 pF
capacitor at RXO (in Figure 1) filters out high frequency
components in the receive path. This helps minimize
high frequency acoustic feedback problems which may
occur if the filter were not present. The filter's insertion
loss is 1.5 dB at 1.0 kHz. The outputs of the attenuators
are inverted from their inputs. Referring to the attenuator
Tx-Rx
Comp
Transmit
Transmit
Receive
Receive
Transmit
Det
Comp
Transmit
Idle
Transmit
Idle
Volume
Control
No Effect
No Effect
Affects ΔVacf
Affects ΔVacf
Δ Vacf
6.0 mV
75 mV
50-150 mV
50-150 mV
Mode
Transmit
Idle
Receive
Receive
As can be seen from the truth table, the Tx-Rx com-
parator dominates. The Transmit Detector Comparator is
effective only in the transmit mode, and the Volume
Control is effective only in the receive mode.
The Tx-Rx comparator is in the transmit position when
there is sufficient transmit signal present over and above
any receive signal. The Transmit Detector Com- parator
then determines whether the transmit signal is a result of
background noise (a relatively stable signal), or speech
which consists of bursts. If the signal is due to
background noise, the attenuators will be put into the idle
mode (AVacf = 75 mV). If the signal consists of speech,
the attenuators will be switched to the trans- mit mode
(AVacf = 6.0 mV.) A further explanation of this function
will be found in the section on the Transmit Detector
Circuit.
The Tx-Rx comparator is in the receive position when
there is sufficient receive signal to overcome the back-
ground noise AND any speech signals. The AVacf volt-
age will now be 150 mV IF the volume control is at the
maximum position, i.e. VLC (Pin 24) = VB. IF VLC is
less than VB, the gain of the receive attenuator, and the
attenuation of the transmit attenuator, will vary in a
complementary manner as shown in Figure 5. It can be
seen that at the minimum recommended operating level
(VLC = 0.55 VB) the gain of the transmit attenuator is
actually greater than that of the receive attenuator. The
effect of varying VLC is to vary AVacf, with a resulting
variation in the gains of the attenuators. Figure 6 shows
the gain variations with ΔVacf..
The capacitor at ACF (Pin 25) smooths the transition
between operating modes. This keeps down any "clicks"
in the speaker or transmit signal when the ACF voltage
switches.
The gain separation of the two attenuators can be
reduced from the typical 45 dB by adding a resistor
between Pins 20 (VCC) and 25 (ACF). The effect is a
reduction of the maximum AVacf voltage in the receive
mode, while not affecting AVacf in the transmit mode.
As an example, adding a 12 kQ resistor will reduce
AVacf by approximately 15 mV (to 135 mV), decrease
the gain of the receive attenuator by approximately 5.0
dB, and increase the gain of the transmit attenuator by a
2011, March, Rev. 01

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KL34018 pdf, datenblatt
KL34018
SWITCHING TIME
The switching times of the speakerphone circuit depend
not only on the various external components, but also on
the operating condition of the circuit at the time a change
is to take effect. For example, the switching time from
idle to transmit is generally quicker than the switching
time from receive to transmit (or transmit to receive).
The components which most significantly affect the
timing between the transmit and receive modes are those
at Pins 5 (transmit turn-on), 6 (transmit turn-off), 7
(receive turn-on), and 8 (receive turn-off). These four
timing functions are not independent, but interact since
the Tx-Rx comparator operates on a RELATIVE Tx-Rx
comparison, rather than on absolute values. The
components at Pins 11, 12, 13, and 23 affect the timing
from the transmit to the idle mode. Timing from the idle
mode to transmit mode is relatively quick (due to the
quick charging of the various capacitors), and is not
greatly affected by the component values. Pins 5-8 do
not affect the idle-to-transmit timing since the Tx-Rx
comparator must already be in the transmit mode for this
to occur.
The following table provides a summary of the effect on
the switching time of the various components, including
the volume control :
Additionally, the following should be noted:
1) The RCs at Pins 5 and 7 have a dual function in that
they affect the sensitivity of the respective log amplifiers,
or in other words, how loud the speech must be in order
to gain control of the speakerphone circuit.
2) The RC at Pin 13 also has a dual function in that it
determines the sensitivity of the transmit detector circuit.
3) The volume control affects the switching speed, and
the relative response to transmit signals, in the following
manner: When the circuit is in the receive mode,
reducing the volume control setting increases the signal
at TXO, and consequently the signal to the TLI pin.
Therefore a given signal at TXI will switch the circuit
into the transmit mode quicker at low volume settings.
The photographs of Figures 16 and 17 indicate
experimentally obtained switching response times for the
circuit of Figure 1. In Figure 16, the circuit is provided a
continuous receive signal of 1.1 mVp-p at RXI (trace
#3). A repetitive burst signal of 7.2 mVp-p, lasting 120
milliseconds, and repeated every 1 second, is applied to
MCI (Trace #I). Trace #2 is the output at TXO, and is
approximately 650 mVp-p at its maximum. Trace #4 is
the output at RXO, and is approximately 2.2 mVp-p at
its maximum. The time to switch from the receive mode
to the transmit mode is approximately 40 ms, as
indicated by the time required for TXO to turn on, and
for RXO to turn off. After the signal at MCI is shut off,
the switching time back to the receive mode is
approximately 210 ms.
In Figure 17, a continuous signal of 7.6 mVp-p is
applied to MCI (Trace #I), and a repetitive burst signal
of 100 mVp-p is applied to RXI (Trace #3), lasting
approximately 120 ms, and repeated every 1 second.
Trace #2 is the output at TXO and is approximately 90
mVp-p at its maximum, and Trace #4 indicates the output
at RXO, and is approximately 150 mVp-p at its
maximum. In this sequence, the circuit switches between
the idle and receive modes. The time required to switch
from idle to receive is approximately 70 ms, as indicated
by the first part of Traces 2 and 4. After the receive
signal is shut off, the time to switch back to the idle mode
is approximately 100 ms.
All of the above mentioned times will change
significantly by varying the amplitude of the input
signals, as well as by varying the external components.
2011, March, Rev. 01

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