KL34018

TECHNICAL DATA
LINEAR INTEGRATED CIRCUIT
KL34018
VOICE SWITCHED SPEAKER PHONE CIRCUIT
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.
KL34018N Plastic
KL34018D/DW SOIC
ORDERING INFORMATION
Device
Operating
Temperature Range
Package
Packing
KL34018N
KL34018D
KL34018DT
TA = -25 to 85 C
DIP28
SOP28
SOP28
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
-1.0 to +12
V
CS (pin 18)
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
Internal Block Diagram
TRANSMIT
CHANNEL
MIC
TRANSMIT
OUTPUT
TRANSMIT
ATTENUATOR
MIC AMP
TRANSMIT
LEVEL
DETECTOR
SIGNAL/NOISE
DETECTOR
TRANSMIT/
RECEIVE
COMPARATOR
ATTENUATOR
CONTROL
SIDE
TONE
SIDE
TONE
RECEIVE LEVEL
DETECTOR
PEAK
LIMITER
SPEAKE
R AMP
RECEIVE
ATTENUATOR
RECEIVE
INPUT
RECEIVE
CHANNEL
VCC
REGULATOR
SPE
AKE
R
DC INPUT
TELEPHONE
LINE
Contek
ENABLE
INPUT
RECEIVE VOLUME
CONTROL
S1
T
0.01F
4.7k
Hook
Switch
0.05F
0.01F
47k
22k
4700pF 4700pF
47k
8.2k
2.2k
F
33k
F
470k
F
R
F 15k
6.8k
8.2k
F
8.2k
47k
47k
F
2.7k
470k
68k
470k
220k
Vcc
F
3.3k
2k
F
MIC
F

X
C

MCI

SKO

SKG

XD

0.1F
0.068F
F
100k
4.7k

F
F
S
F
VB
F
3.3k







TXO
TLI
CP1
ACF
AGC
V+
CS
RLI

RTX
RR
RRX
RXO
SKI
CP2
XDC
TLO







RXI
F

4.3k
VB
91k
30k
18k
Volume
Control
F
24k
F
F
20k
200k
RLO
GND

2.2M

2.2M
F

F
Vcc

F
VB

F
VLC
F
Speaker
Fig 1 - Basic Line powered Speakerphone
2011, March, Rev. 01
KL34018
PIN CONFIGURATIONS
PIN NAME
1
RR
2
RTX
3
4
TXI
TXO
5
TLI
6
TLO
7
RLI
8
RLO
9
MCI
10
11
MCO
CP1
12
CP2
13
XDI
14
SKG
15
SKO
16
V+
17
AGC
18
CS
19
20
21
SKI
VCC
VB
22
23
GND
XDC
24
VLC
25
ACF
26
27
28
RXO
RXI
RRX
DESCRIPTION
A resistor to ground provides a reference current for the transmit and receive attenuators
A resistor to ground determines the nominal gain of the transmit attenuator ,the transmit channel gain is
inversely proportional to RTX resistance.
Input to the transmit attenuator. Input resistance is nominally 5.0k ohms.
Output of the transmit attenuator. The TXO output signal drivers the input of transmit level detcetor, as well
as the external circuit which drivers the telephone line.
Input of the transmit level detector. An external resistor ac coupled to The TLI pin sets the detection level.
Decreasing this resistor increases the sensitivity to transmit channel signals.
Output of the transmit level detector. The external resistor and capacitor set the time the comparator will
hold the system in the transmit mode after speech ceases.
Input of the receive level detector. An external resistor ac coupled to The RLI pin sets the detection level.
Decreasing this resistor increases the sensitivity to receive channel signals
Output of the receive level detector. The external resistor and capacitor set the time the comparator will
hold the system in the receive mode after speech ceases
Microphone amplifier input. Input impedance is nominally 10k ohms and the dc bias voltage is
approximately equal to VB
Microphone amplifier output. The MIC amp gain is internally set at 34dB(50V/V)
A parallel resistor and capacitor connected between this pin and VCC holds a voltage corresponding
to the background noise level. The transmit detector compares the CP1 voltage with the speech signal from
CP2.
A capacitor at this pin peak detects the speech signals for comparison with the background noise level held
at CP1.
Input to the transmit detector system. The microphone amplifier output is ac coupled to the XDI pin
through an external resistor
High current ground pin for the speaker amplifier output stage. The SKG voltage should be within
10mV of the ground voltage at pin 22
Speaker amplifier output. The SKO pin will source and sink up to 100mA when ac coupled to the
speaker. The speaker amplifier gain is internally set at 34dB(50V/V).
Input DC supply voltage. V+ can be powered from Tip and Ring if an ac decoupling inductor is used to
prevent loading ac line signals. The required V+ voltage is 6.0V to 11V(7.5V nominal ) at 7.0mA
A capacitor from this pin to VB stabilizes the speaker amplifier gain control loop, and additionally
controls the attack and decay time of this circuit. The gain control loop limits the speaker amplifier input
to prevent clipping at SKO. The internal resistance at AGC pin is nominally 110k ohms.
Digital chip select input. When at a logic "0" (<0.7V) the VCC regulator is enabled. When at a logic "1"
(>1.6V),the chip is in the standby mode drawing 0.5mA.An open CS pin is a logic "0". Input
Impedance is nominally 140k ohms. The input voltage should not exceed 11V
Input to the speaker amplifier. Input impedance is nominally 20k ohms
A 5.4V regulated output which powers all circuits except the speaker amplifier output stage
An output voltage equal to approximately VCC/2 which series as an analog ground for the
speakerphone system. Up to 1.5mA of external load current may be sourced from VB. Output
impedance is 250 ohms. A filter capacitor is required
Ground pin for the IC(except the speaker amplifier)
Transmit detector output. A resistor and capacitor at his pin hold the system in the transmit mode during
pauses between words or phrases. When the XDC pin voltage decays to ground, the attenuators switch
from the transmit mode to idle mode. The internal resistor at XDC is nominally 2.6k ohms(see fig.1).
Volume control input>connecting this pin to the slider of a variable resistor provides receive mode
volume control. The VLC pin voltage should be less than or equal to VB
Attenuator control filter. A capacitor connected to this pin reduces noise transient as the attenuator
control switches level of attenuation
Output of the receive attenuator. Normally this pin is ac coupled to the input of the speaker amplifier
Input of the receive attenuator. Input impedance is nominally is 5.0k ohms
A resistor to ground determines the nominal gain of the receive attenuator. The receive channel gain is
directly proportional to the RRX resistance
2011, March, Rev. 01
KL34018
ELECTRICAL CHARACTERISTICS (referred to fig. 1)
PARAMETER
SUPPLY VOLTAGES
V+ Supply Current
V+=11V, Pin 18=0.7V
V+=11V, Pin 18=1.6V
VCC Voltage (V+=7.5V)
Line
Regulation (6.5V<V+<11V)
Output Resistance (ICC=3mA)
VB Voltage(V+=7.5V)
Output Resistance (I B=1.7mA)
ATTENUATORS
Receive Attenuator Gain (1.0kHz)
Rx Mode, Pin 24= VB, Pin 27 =
250Mvrms
Range (Rx to Tx Modes)
Idle Mode, Pin 27= 250mVrms
RXO Voltage (Rx Mode)
Delta RXO Voltage (Switch from Rx
to Tx Mode)
RXO Sink Current (Rx mode)
TXO Source Current (Tx mode)
TXO Input Resistance
ACF Voltage (VCC-Pin 25 Voltage)
Rx Mode
Tx Mode
Idle Mode
SPEAKER AMPLIFIER
Speaker Amp Gain (pin 19 = 20mVrms)
SKI Input Resistance
SKO Voltage ( Pin 19 =Cap couple
to GND)
SKO High Voltage ( Pin 19 = 0.1V,
-100mA Load at Pin 15)
SKO Low Voltage (pin 19=0.1V,
+100mA Load at Pin 15)
MICROPHONE AMPLIFIER
Microphone Amp Gain
( Pin 9 = 10mVrms,1KHz)
Microphone Amp Input Resistance
LOGAMPS
RLO Leakage Current (Pin 8 = VB+1.0V)
TLO Leakage Current (Pin 6 = VB+1.0V)
Transmit-Receive Switching
Threshold (Ratio of ITLI to IRLI - at
20 A - to Switch Tx-Rx Comparator)
SYMBOL
MIN
TYP
MAX
UNIT
9.0
800
5.9
150
20
300
3.3
mA
A
Vdc
MV
ohms
mV
Vdc
ohms
IV+
Vcc
VccLN
RoVcc
Vccsat
Vb
Rovb
4.9
GRX
2.0
6.0
10
dB
GRX
GRI
VRXO
VRXO
40
-20
1.8
44
-16
2.3
48
-12
3.2
100
dB
dB
mV
mV
IRXOL
ITXOH
RTXI
VACF
75
1.0
3.5
3.0
8.0
A
mA
k
2.5
5.4
65
6.0
80
2.9
250
5.0
150
6.0
75
GSPK
RSKI
VSKO
33
15
2.4
VSKOH
5.5
34
22
3.0
mV
mV
mV
35
37
3.6
dB
k
Vdc
Vdc
VSKOL
600
mV
GMCI
32.5
34
35
dB
RMCI
6.5
10
16
k
2.0
2.0
A
A
ILKRLO
ILKTLO
ITH
25
2011, March, Rev. 01
KL34018
ELECTRICAL CHARACTERISTICS (continued)
PARAMETER
SYMBOL
MIN
TYP
5.0
0
4.0
10
MAX
UNIT
TRANSMIT DETECTOR
XDC Voltage
Idle Mode
Tx Mode
CP2 Current Source
Distortion
Rx Mode
RXI to SKO
(pin 27 = 10mVrms,1KHz)
Tx Mode
MCI to TXO
(Pin 9 = 5mVrms,1KHz)
VXDC
ICP2
Vdc Vdc
13
A
RXD
1.5
%
TXD
2.0
%
Note 1:V+=7.5V, CS =0.7V except where noted.
Note 2:Rx mode:pin7=-100 A, pin5=+100 A, except where noted
Tx mode: pin 5,13=-100 A, pin 7=+100 A, pin 11=0V. Idle mode: Pin 5=-100A, pin 7,13=+100 A
Note 3:Current into a pin designed as + ,current out of a pin designed -;
Note 4:Voltage referred to pin 22,Tamb=25 C
TEMPERATURE CHARACTERISTICS (-20 TO +60℃ )
PARAMETER
PIN
TYP CHANGE
UNIT
V+ Supply Current ( V+ 11V,Pin 18 = 0.7V )
16
-0.2
%/ C
V+ Supply Current(V+ 11V,Pin 18 = 1.6V )
16
-0.4
%/ C
VCC Voltage( V+ = 7.5V )
20
+0.1
%/ C
+-0.003
dB/ C
Attenuator Gain ( Max and Min Setting )
Delta RXO,TXO Voltage
4,26
+-0.24
%/ C
Speaker AMP Gain
15,19
+-0.001
dB/ C
Microphone AMP Gain
9,10
+-0.4
dB/ C
Microphone Amp Input Resistance
9
+0.4
%/ C
Tx-Rx Switching Threshold (20 A)
5,7
+-0.2
nA/ C
2011, March, Rev. 01
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
Volume
Δ Vacf
Det
Control
Comp
Transmit
No Effect
6.0 mV
Idle
No Effect
75 mV
Transmit Affects ΔVacf 50-150 mV
Idle
Affects ΔVacf 50-150 mV
Mode
Transmit
Idle
Receive
Receive
As can be seen from the truth table, the Tx-Rx comparator 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 background noise AND any speech signals. The AVacf voltage 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
KL34018
control block, the AVacf voltage at its output is
determined by three inputs. The relationship of the
inputs and output is summarized in the following truth
table:
LOG AMPLIFIERS
(Transmit and Receive Level Detectors)
The log amps monitor the levels of the transmit and
receive signals, so as to tell the Tx-Rx comparator which
mode should be in effect. The input signals are applied
to the amplifiers (at TLI and RLI) through AC coupling
capacitors and current limiting resistors. The value of
these components determines the sensitivity of the
respective amplifiers, and has an effect on the switching
times between transmit and receive modes. The feedback
elements for the amplifiers are back-to-back diodes
which provide a logarithmic gain curve, thus allowing
operation over a wide range of signal levels. The outputs
of the amplifiers are rectified, having a quick rise time
and a slow decay time. The rise time is determined
primarily by the external capacitor (at TLO or RLO) and
an internal 500 ohm resistor, and is on the order of a
fraction of a millisecond. The decay time is determined
by the external resistor and capacitor, and is on the order
of a fraction of a second. The switching time is not
fixed, but depends on the relative values of the transmit
and receive signals, as well as these external
components. Figure 7 indicates the dc transfer
characteristics of the log amps, and Figure 8 indicates
the transfer characteristics with respect to an ac input
signal. The dc level at TLI, RLI, TLO, and RLO is
approximately VB.
The Tx-Rx comparator responds to the voltages at TLO
and RLO, which in turn are functions of the currents
sourced out of TLI and RLI, respectively. If an offset at
the comparator input is desired, e.g., to prevent noise
from switching the system, or to give preference to either
the transmit or receive channel, this may be achieved by
biasing the appropriate input (TLI or RLI). A resistor to
ground will cause a DC current to flow out of that input,
thus forcing the output of that amplifier to be biased
slightly higher than normal. This amplifier then becomes
the preferred one in the system operation. Resistor
values from 500 k to 10 M ohms are recommended for
this purpose.
SPEAKER AMPLIFIER
The speaker amplifier has a fixed gain of 34 dB (50
VN), and is noninverting. The input impedance is
nominally 22 kR as long as the output signal is below
that required to activate the Peak Limiter. Figure 9
indicates the typical output swing available at SKO (Pin
15). Since the output current capability is 100 mA, the
lower curve is limited to a 5.0 volt swing. The output
impedance depends on the output signal level and is
relatively low as long as the signal level is not near the
maximum limits. At 3 volts p-p the output impedance is
similar amount. If the circuit requires the receive
attenuator gain to be +6.0 dB in the receive mode, RRX
must be adjusted (to - 27 k) to re-establish this value.
This change will also increase the receive attenuator gain
in the transmit mode by a similar amount. The resistor at
TLI may also require changing to reset the sensitivity of
the transmit level detector.
effect is that of a gain reduction caused by a reduction of
the input impedance (at SKI) to a value not less than 2.0
㏀.
The capacitor at Pin 17 (AGC) determines the response
time of the peak limiter circuit. When a large input signal
is applied to SKI, the voltage at AGC (Pin 17) will drop
quickly as a current source is applied to the external
capacitor. When the large input signal is reduced, the
current source is turned off, and an internal 110 ㏀
resistor discharges the capacitor so the voltage at AGC
can return to its normal value (1.9 Vdc). The capacitor
additionally stabilizes the peak limiting feedback loop.
If there is a need to mute the speaker amplifier without
disabling the rest of the circuit, this may be accomplished
by connecting a resistor from the AGC pin to ground. A
100 kfl resistor will reduce the gain by 34 dB (0 dB from
SKI to SKO), and a 10 k resistor will reduce the gain by
almost 50 dB.
TRANSMIT DETECTOR CIRCUIT
The transmit detector circuit, also known as the
background noise monitor, distinguishes speech (which
consists of bursts) from the background noise (a
relatively constant signal). It does this by storing a
voltage level, representative of the average background
noise, in the capacitor at CP1 (Pin 11). The resistor and
c a p a c i t o r a t t h i s p i n h a v e a t ime co nstant o f
approximately 5 seconds (in Figure 1). The voltage at Pin
11 is applied to the inverting input of the Transmit
Detector Comparator. In the absence of speech signals,
the noninverting input receives the same voltage level
minus an offset of 36 mV. In this condition, the output of
the comparator will be low, the output transistor turned
off, and the voltage at XDC (Pin 23) will be at ground. If
the Tx-Rx comparator is in the transmit position, the
attenuators will be in the idle mode (AVacf=75 mV).
When speech is presented to the microphone, the signal
burst appearing at XDI reaches the noninverting input of
the transmit detector comparator before the voltage at the
inverting input can change, causing the output to switch
high, driving the voltage at XDC up to approximately 4
volts. This high level causes the attenuator control block
to switch the attenuators from the idle mode to the
transmit mode (assuming the Tx-Rx comparator is in
the transmit mode). As long as the speech continues to
arrive, and is maintained at a level above the background,
the voltage at XDC will be maintained at a high level,
and the circuit will remain in the transmit mode. The time
constant of the components at XDC will determine how
much time the circuit requires to return to the idle mode
after the cessation of microphone speech signals, such as
2011, March, Rev. 01
KL34018
<0.5 ohms, and at 4.5 volts p-p it is <3 ohms. The output
is short circuit protected at approximately 300 rnA.
When the amplifier is overdriven, the peak limiter
causes a portion of the input signal to be shunted to
ground, in order to maintain a constant output level. The
greater than the change at CP2). Increasing the resistor,
or lowering the capacitor, will reduce the response at
these pins. The first amplifier (between XDI and CP2) is
logarithmic in order that this circuit be able to handle a
wide range of signal levels (or in other words, it
responds equally well to people who talk quietly and to
people who shout). Figure 7 indicates the dc transfer
characteristics of the log amp.
Figure 11 indicates the response at Pins 11, 12, and 23
to a varying signal at the microphone. The series of
events in Figure 11 is as follows:
1) CP2 (Pin 12) follows the peaks of the speech
signals, and decays at a rate determined by the 10pA
current source and the capacitor at this pin.
2) CP1 (Pin 11) increases at a rate determined by the
RC at this pin after CP2 has made a positive transition. It
will follow the decay pattern of CP2.
3) The noninverting input of theTransmit Detector
Comparator follows CP2, gained up by 2.7, and reduced
by an offset of 36 mV. This voltage, compared to CP1,
determines the output of the comparator.
4) XDC (Pin 23) will rise quickly to 4 Vdc in response
to a positive transition at CP2, but will decay at a rate
determined by the RC at this pin. When XDC is above
3.25 Vdc, the circuit will be in the transmit mode. As it
decays towards ground, the attenuators are taken to the
idle mode.
MICROPHONE AMPLIFIER
The microphone amplifier is noninverting, has an
internal gain of 34 dB (50 VN), and a nominal input
impedance of 10 kR. The output impedance is typically
<15 ohms. The maximum p-p voltage swing available at
the output is approximately 2.0 volts less than VCC,
which is substantially more than what is required in-most
applications.
The input at MCI (Pin 9) should be ac coupled to the
microphone so as to not upset the bias voltage.
Generally, microphone sensitivity may be adjusted by
varying the 2 k microphone bias resistor, rather than by
attempting to vary the gain of the amplifier.
POWER SUPPLY
The voltage supply for the KL34018 at V+ (Pin 16)
should be in the range of 6.0 to 11 volts, although the
supply. The required supply current, with no signal to
the speaker, is shown in Figure 12. The upper curve
indicates the normal operating current when - Chip
Select (Pin 18) is at a Logic "0". Figure 13 indicates the
average dc current required when supplying various
power levels to a 25 ohm speaker. Figure 13 also
indicates the minimum supply voltage required to
provide the indicated power levels. The peak in the
power supply current at 5.0-5.4 volts occurs as the VCC
occurs during the normal pauses in speech.
The series resistor and capacitor at XDI (Pin 13)
determine the sensitivity of the transmit detector circuit.
Figure 10 indicates the change in DC voltage levels at
CP2 and CP1 in response to a steady state sine wave
applied at the input of the 0.068 pF capacitor and 4700
ohm resistor (the voltage change at CP1 is 2.7 times
variation at V+ caused by the required speaker current
flowing through this pin can cause a low frequency
oscillation. The result is usually that the circuit will cut
the speaker signal on and off at the rate of a few hertz.
Experiments have shown that only a few inches of wire
between the supply and the IC can cause the problem if
the filter capacitor is not physically adjacent to the IC. It
is equally imperative that both ground pins [Pins 14 and
22) have a low loss connection to the power supply
ground.
Vcc
VCC (Pin 20) is a regulated output voltage of 5.4 volts,
+I - 0.5 V. Regulation will be maintained as long as V +
is (typically) 80 mV greater than the regulated value of
VCC. Up to 3 milliamps can be sourced from this supply
for external use. The output impedance is <20 ohms.
The 47 pF capacitor indicated for connection to Pin 20
is essential for stability reasons. It must be located
adjacent to the IC.
If the circuit is deselected (see section on Chip Select),
the VCC voltage will go to 0 volts.
If the KL34018 is to be powered from a regulated
supply (not the Tip and Ring lines) of less than 6.5 volts,
the configuration of Figure 14 may be used so as to
ensure that VCC is regulated. The regulated voltage is
applied to both V+ and VCC, with CS held at a Logic
"1" so as to turn off the internal regulator (the Chip
Select function is not available when the circuit is used in
this manner). Figure 15 indicates the supply current used
by this configuration, with no signal at the speaker. When
a signal is sent to the speaker, the curves of Figure 13
apply.
VB
VB is a regulated output voltage with a nominal value
of 2.9 volts, +I-0.4 volts. It is derived from VCC and
tracks it, holding a value of approximately 54% of VCC.
1.5 milliamps can be sourced from this supply at a typical
output impedance of 250 ohms.
The 47 pF capacitor indicated for connection to the VB
pin is required for stability reasons, and must be adjacent
to the IC.
If the circuit is deselected (see section on Chip Select),
the VB voltage will go to 0 volts. circuit will operate
down to 4.0 volts. The voltage can be supplied either
from Tip and Ring, or from a separate
CHIP SELECT
The Chip Select pin (Pin 18) allows the chip to be
shown in Figure 12. The input resistance at Pin 18 is
powered down anytime its functions are not required.
2011, March, Rev. 01
KL34018
circuit comes into regulation.
It is imperative that the V+ supply (Pin 16) be a good
ac ground for stability reasons. If this pin is not well
filtered (by a 1000 pF capacitor AT THE IC), any
>75 ㏀. The VCC and VB regulated voltages go to 0.0 A
Logic "1" level in the range of 1.6 V to 11 V deselects
when the chip is deselected. Leaving Pin 18 open is the
chip, and the resulting supply current (at V+) is
equivalent to a Logic "0" (chip enabled).
2011, March, Rev. 01
KL34018
2011, March, Rev. 01
KL34018
2011, March, Rev. 01
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.
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.
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
2011, March, Rev. 01
KL34018
Components
RC @ Pin 5
RC @ Pin 6
RC @ Pin 7
RC @ Pin 8
RC @ Pin 11
C @ Pin 12
RC @ Pin 13
RC @ Pin 23
V @ Pin 24
C @ Pin 25
Tx to Rx
Moderate
Significant
Significant
Moderate
No effect
No effect
No effect
No effect
No effect
Moderate
Rx to Tx
Significant
Moderate
Moderate
Significant
Slight
Slight
Slight
Slight
Moderate
Moderate
Tx to Idle
No effect
No effect
No effect
No effect
Moderate
Significant
Slight
Significant
No effect
Slight
2011, March, Rev. 01
KL34018
N SUFFIX PLASTIC DIP
(MS - 001AB)
Dimension, mm
A
15
28
B
1
14
Symbol
MIN
MAX
A
35.10
39.70
B
12.32
14.73
C
F
6.35
D
0.36
0.56
F
0.77
1.78
L
C
G
2.54
H
15.24
-T- SEATING
PLANE
N
G
K
M
H
D
J
J
0
10
K
2.92
5.08
L
15.24
15.87
M
0.20
0.38
N
0.38
0.25 (0.010) M T
NOTES:
1. Dimensions “A”, “B” do not include mold flash or protrusions.
Maximum mold flash or protrusions 0.25 mm (0.010) per side.
D SUFFIX SOIC
(MS - 059AD)
Dimension, mm
A
28
Symbol
MIN
MAX
A
17.70
18.50
B
7.40
7.60
C
2.35
3.05
D
0.35
0.50
F
0.40
1.27
15
B
H
1
P
14
G
R x 45
C
-TK
D
SEATING
PLANE
0.25 (0.010) M T C M
NOTES:
1. Dimensions A and B do not include mold flash or protrusion.
2. Maximum mold flash or protrusion 0.15 mm (0.006) per side
for A; for B ‑ 0.25 mm (0.010) per side.
J
F
G
1.27
H
11.43
M
J
0
8
K
0.05
0.35
M
0.14
0.32
P
10.00
10.65
R
0.25
0.75
2011, March, Rev. 01