UTCMC34018 데이터 시트보기 (PDF) - Unisonic Technologies
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UTCMC34018 Datasheet PDF : 14 Pages
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UTCMC34018 LINEAR INTEGRATED CIRCUIT
If UTC MC34018 is to be powered from a regulated supply( not the Tip and Ring lines) of less than 6.5 volts,
the configuration of Fig 14 may be used so as to ensure to 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).Fig 15 indicates the supply current used by the configuration, with
no signal at the speaker. When a signal is sent to the speaker, the curves of Fig 13 apply.
VB
VB is a regulated output voltage with a nominal value of 2.9 +-0.4volts.It is derived from VCC and tracks it,
holding a value of approximately 54% of VCC.1.5milliamps can be sourced from this supply at a typical output
impedance of 250 ohms.
The 47µF 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.
CHIP SELECT
The CS pin allows the chip to be powered down anytime its functions are not required. A logic "1" level in the
range of 1.6V to 11V deselects the chip and the resulting supply current (at V+) is shown in Fig 12.The input
resistance at pin CS is greater than 75 k ohms. The VCC and VB regulated voltage go to 0 volts when the chip is
deselected. Leaving Pin 18 open is equivalent to a logic "0"(chip enabled).
SWITCH TIME
The switch time of the speakerphone circuit depend not only the various external components, but also on the
operating condition of the circuit at the time a change os taken effect. For example, the switching time form 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),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 value. The components at pins 11,12,13,23 affect the timing from the transmit mode 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. Pin 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:
COMPONENTS
RC@pin5
RC@pin6
RC@pin7
RC@pin8
RC@pin11
C@pin12
RC@pin13
RC@pin23
V@pin24
C@pin25
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
Additionally ,the following should be noted:
1) RCs at pin 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 speaker phone circuits.
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 the transmit signals, in 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.
All of the above mentioned times will change significantly by varying the amplitude of the input signals, as well
UTC UNISONIC TECHNOLOGIES CO., LTD. 9
QW-R108-006,A
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