KL34018 IK Semicon Co., Ltd, KL34018 Datasheet - Page 11

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

SWITCHING TIME
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).
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 switching times of the speakerphone circuit
The components which most significantly affect the
on the switching time of the various components,
including the volume control :
Additionally, the following should be noted:
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.
determines the sensitivity of the transmit detector circuit.
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.
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
The photographs of Figures 16 and 17 indicate
The following table provides a summary of the effect
2) The RC at Pin 13 also has a dual function in that it
3) The volume control affects the switching speed, and
1) The RCs at Pins 5 and 7 have a dual function in that
Rev. 00
KL34018