MC34018L-R28-R datasheet(3/8 Pages) UTC

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MC34018

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

3 of 8

www.unisonic.com.tw

QW-R108-006,C

PIN DESCRIPTION(Cont.)

PIN NO.

PIN NAME

DESCRIPTION

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).

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.

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.

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.

SKI

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

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".

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.

GND

Ground pin for the IC(except the speaker amplifier)

XDC

Transmit detector output. A resistor and capacitor at his 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 from the transmit mode to idle mode. The internal resistor at

XDC is nominally 2.6k ohms(see Fig.1).

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.

ACF

Attenuator control filter. A capacitor connected to this pin reduces noise transient as the

attenuator control switches level of attenuation.

RXO

Receive attenuator Output. Normally this pin is ac coupled to the input of the speaker

amplifier.

RXI

Receive attenuator Input. Input impedance is nominally is 5.0kΩ.

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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