KL34018 IK Semicon Co., Ltd, KL34018 Datasheet - Page 8

• Manufacturer Part Number: KL34018
• Description: Linear Integrated Circuit Voice Switched Speaker Phone Circuit
• Manufacturer: IK Semicon Co., Ltd

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.
to a varying signal at the microphone. The series of
events in Figure 11 is as follows:
signals, and decays at a rate determined by the 10pA
current source and the capacitor at this pin.
RC at this pin after CP2 has made a positive transition.
It will follow the decay pattern of CP2.
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.
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
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.
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
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
circuit comes into regulation.
ac ground for stability reasons. If this pin is not well
filtered (by a 1000 pF capacitor AT THE IC), any
Figure 11 indicates the response at Pins 11, 12, and 23
The microphone amplifier is noninverting, has an
The input at MCI (Pin 9) should be ac coupled to the
The voltage supply for the KL34018 at V+ (Pin 16)
It is imperative that the V+ supply (Pin 16) be a good
1) CP2 (Pin 12) follows the peaks of the speech
2) CP1 (Pin 11) increases at a rate determined by the
3) The noninverting input of theTransmit Detector
4) XDC (Pin 23) will rise quickly to 4 Vdc in response
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
+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.
is essential for stability reasons. It must be located
adjacent to the IC.
the VCC voltage will go to 0 volts.
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
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.
pin is required for stability reasons, and must be adjacent
to the IC.
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
shown in Figure 12. The input resistance at Pin 18 is
powered down anytime its functions are not required.
>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).
If the KL34018 is to be powered from a regulated
If the circuit is deselected (see section on Chip Select),
VB is a regulated output voltage with a nominal value
The 47 pF capacitor indicated for connection to the VB
If the circuit is deselected (see section on Chip Select),
The Chip Select pin (Pin 18) allows the chip to be
VCC (Pin 20) is a regulated output voltage of 5.4 volts,
The 47 pF capacitor indicated for connection to Pin 20
Rev. 00
KL34018