MC34118 VOICE SWITCHED SPEAKERPHONE CIRCUIT

MC34118

VOICE SWITCHED SPEAKERPHONE CIRCUIT

The MC34118 Voice Switched Speakerphone Circuit incorporates the

nessesary amplifier, attenuators, level detectors, and control algorithm to

form the heart for a high quality hands-free speacerphone system . Included

are a microphone amplifier with adjustable gain and MUTE control. Transmit

and Receive attenuators which operate in a complementary manner, level

detectors at both input and output of both attenuators, and background

noise monitors for both the transmit and receive channals. A Dial Tone

Detector prevents the dial tone fom being attenuated by the Receive

baskgrounds noise monitor circuit. Also included are two line drive

ampifiers which can be used to form a hybrid network in conjunction with an

external coupling transforsmer. A high-pass filter can be used to filter

out 60Hz noise in the receive channel, or for other filtering functions. A

Chip Disable pin permits powering down the entire circuit to conserve power

on long loops where loop current is at a minimum.

The MC34118 may be operated from a power supply, or it can be powered

from the telephone line, requiring typically 5mA. The MC34118 can be

interfaced directly to Tip and Ring (thought a coupling transformer) for

stand-alone operation, or it can be used in cojunction with a handset

speech network and/or other features of a featurephone.

FEATURES

- Improved Attenuator Gain Range: 52dB Between Transmit and Receive

- Low Voltage Operation for Line-Powered Applications (36,5V)

- 4-Point Signal Sencing for Improved Sencitivity

- Background Noise Monitors for Both Transmit and Receive Parts

- Microphone Amplifier Gain Set by External Resistors - Mute Function

Included

- Chip Disable for Active/Standby Operation

- On Board Filter Pinned-Out for User Defined Function

- Dial Tone Detector to Inhibit Receive Idle Mode during Dial Tone

Presence

- Standart 28-Pin Plastic DIP Package and SOIC Package Avaible

- Compatible with MC34119 Speaker Amplifier

ABSOLUTE MAXIMUM RATING

Supply Voltage (Pin4) -1,+7V

Voltage at CD (Pin3), MUT (Pin12) -1,Vcc+1V

Volage at VLC (Pin13) -1,Vcc+0,5V

Voltage at TXI (Pin9), RXI (Pin21), FI (Pin2) -0,5;Vcc+0,5V

RECOMMENDED OPERATING LIMITS Min Typ Max

Supply Limits (Pin4) 3,5Vdc - 6,5Vdc

CD Input (Pin3), MUT (Pin12) 0 - Vcc

Ivb Current (Pin15) - - 500mkA

VLC (Pin13) 0,3xVb - Vb,Vdc

Attenuator Input Signal Voltage (Pin9,21) 0 - 350mVrms

Microphone Amplifier, Hibrid Amplifier Gain 0 - 40dB

Load Current @ RXO, TXO (Pin8,22) 0 - -+2mA

@ MCO(Pin10) 0 - -+1mA

@ HTO-, HTO+ (Pin6,5) 0 - -+5mA

Ambient Temperature Range -20C - +60C