MC34018

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

3 of 8

www.unisonic.com.tw

QW-R108-006.E



PIN DESCRIPTION

PIN NO.

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 RTX resistance.

3

TXI

Transmit Attenuator Input, Input resistance is nominally 5.0kΩ.

4

TXO

Transmit Attenuator Output, The TXO output signal drivers the input of transmit level

detcetor, as well as the external circuit which drivers the telephone line.

5

TLI

Transmit Level detector Input. An external resistor ac coupled to The TLI pin sets the

detection level. Decreasing this resistor increases the sensitivity to transmit channel

signals.

6

TLO

Transmit Level detector Output. The external resistor and capacitor set the time the

comparator will hold the system in the transmit mode after speech ceases.

7

RLI

Receive Level detector Input. An external resistor ac coupled to The RLI pin sets the

detection level. Decreasing this resistor increases the sensitivity to receive channel signals.

8

RLO

Receive Level detector Output. 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 10kΩ and the dc bias voltage is

approximately equal to VB

10

MCO

Microphone amplifier output. The MIC amp gain is internally set at 34dB (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 amplifier output stage. The SKG voltage should be

within 10mV of the ground voltage at pin 22.

15

SKO

Speaker amplifier output. The SKO pin will source and sink up to 100mA when ac coupled

to the speaker. The speaker amplifier gain is internally set at 34dB (50V/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 6.0V to 11V (7.5V

nominal) at 7.0mA.

17

AGC

A capacitor from this pin to VB stabilizes the speaker amplifier gain control loop, and

additionally controls the attack and decay time of this circuit. The gain control loop limits the

speaker amplifier input to prevent clipping at SKO. The internal resistance at AGC pin is

nominally 110kΩ.

18

CS

Digital chip select input. When at a logic "0" (<0.7V) the VCC regulator is enabled. When at

a logic "1" (>1.6V),the chip is in the standby mode drawing 0.5mA.An open CS pin is a logic

"0".Input impedance is nominally 140k ohms. The input voltage should not exceed 11V.

19

SKI

Input to the speaker amplifier. Input impedance is nominally 20kΩ.

20

VCC

A 5.4V regulated output which powers all circuits except the speaker amplifier output stage.

VCC can be used to power external circuitry such as a microprocessor(3.0mA max.) A filter

capacitor is required. The UTC MC34018 can be powered by a separate regulated supply

by connecting V+ and VCC to a voltage between 4.5V and 6.5V while maintaining CS at a

logic "1".

21

VB

An output voltage equal to approximately VCC/2 which series as an analog ground for the

speakerphone system. Up to 1.5mA 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)