4. PIN CONFIGURATIONS
Pin Name Description
1 RR A resistor to ground provides a reference current for the transmit and receive attenuators.
2 RTX A resistor to ground determines the nominal gain of the transmit attenuator. The transmit
channel gain is inversely proportional to the RTX resistance.
3 TXI Input to the transmit attenuator. Input resistance is nominally 5.0 k ohms.
4 TXO Output of the transmit attenuator. The TXO output signal drives the input of the transmit
level detector, as well as the external circuit which drives the telephone line.
5 TLI 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
6 TLO 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.
7 RLI 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
8 RLO 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.
9 MCI Microphone amplifier input. Input impedance is nominally 10 k ohms and the dc bias
voltage is approximately equal to VB.
10 MCO Microphone amplifier output. The mic amp gain is internally set at 34 dB (50V/V).
11 CP1 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.
12 CP2 A capacitor at this pin peak detects the speech signals for comparison with the
background noise level held at CP1.
13 XDI Input to the transmit detector system. The microphone amplifier output is ac coupled to
the XDI pin through an external resistor.
14 SKG High current ground pin for the speaker amp output stage. The SKG voltage should be
within 10 mV of the ground voltage at Pin 22.
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 (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 6.0 to 11 V
(7.5 V nominal) at 7.0 mA.
17 AGC A capacitor from this pin to VB stabilizes the speaker amp gain control loop and
Total 16 Pages
Wrote by 2006