Panasonic KX-TS2365RUB Service Manual page 67

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15 SKO Speaker amplifier output. The SKO pin will source and sink up to 100 mA when ac coupled to the speaker. The
speaker amp gain is internally set at 34 dB (50 V/V).
16 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 6.0 to 11 V (7.5 V nominal) at7.0 mA.
17 AGC A capacitor from this pin to VB stabilizes the speaker amp gain control loop, and additionally controls the attack
and decay time of this circuit. The gain control loop limits the speaker amp input to preventclipping at SKO. The
internal resistance at the AGC pin is nominally 110 kohms.
18 CS Digital chip select input. When at a Logic "0" (<0.7 V) the Vcc regulator is enabled. When at a Logic "1" (>1.6 V),
the chip is in the standby mode drawing 0.5 mA. An open CS pin is a Logic "0".Input impedance is nominally 140
kohms. The input voltage should not exceed 11 V.
19 SKI Input to the speaker amplifier. Input impedance is nominally 20 kohms.
20 Vcc A 5.4 V regulated output which powers all circuit expect the speaker amplifier output stage. Vcc can be used to
power external circuitry such as a microprocessor (3.0 mA max). A filter capacitor is required. TheMC 34018 can
be powered by a separate regulated supply by connecting V+ and Vcc to a voltage between 4.5 V and 6.5 V while
maintaining CS at a Logic "1".
21 VB An output voltage equal to approximately Vcc/2 which serves as an analogue ground for the speakerphone system.
Up to 1.5 mA of external load current may be sourced from VB. Output impedance is 250 ohms.A filter capacitor
is required.
22 Gnd Ground pin for the IC (except the speaker amplifier).
23 XDC Transmit detector output. A resistor and capacitor at this 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 fromthe transmit
mode to the idle mode. The internal resistor at XDC is nominally 2.6 kohms.
24 VLC 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.
25 ACF Attenuator control filter. A capacitor connected to this pin reduces noise transients as the attenuator control
switches levels of attenuation.
26 RXO Output of the receive attenuator. Normally this pin is ac coupled to the input of the speaker amplifier.
27 RXI Input of the receive attenuator. Input resistance is nominally 5.0 kohms.
28 RRX A resistor to ground determines the nominal gain of the receive attenuator. The receive channel gain is directly
proportional to the RRX resistance.
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