MC34018
VOICE SWITCHED SPEAKERPHONE CIRCUITS
The MC34018 Speakerphone integrated circuit incorporates the nessesary
amplifiers, attenuators, and control functions to produce a high
quality hands-free speakerphone system. Included are a microphone
amplifier, a power audio amplifier for the speaker, transmit and receive
attenuators, a monitoring system for background sound level, and an
attenuator control system which responds to the relative transmit and
receive levels as well as the background level. Also included are all
nessesery regulated voltage for both internal and external circuitry,
allowing line-powered operation (no additional power supplies required). A
Chip Select pin allows the chip to be powered down when not in use. A
volume control function may be implemented with an external
potentiometer. MC34018 applications include speakerphones for household and
business use, intercom systems, automotive telephones, and others.
FEATURES
- All nessesary level detection and attenuation controls for a
hands-free telephone in a single integrated circuit
- Background noise level monitoring with long time constant
- Wide operating dynamic range through signal compression
- On-chip supply and reference voltage regulation
- Typical 100mW output power (into 25 Ohms) with peak limiting to
minimaize distorsion
- Chip Select pin for active/standby operation
- Linear Volume Control Function
- Standart 28-pin plastic DIP package (0.600 inch wide) and SOIC
package
ABSOLUTE MAXIMUM RATINGS
(Voltage refered to Pin22 Ta=25C)
V+ Terminal Voltage (Pin16) +12,-1V
CS (Pin18) +12,-1V
Speaker Amp Ground (Pin14) +3,-1V
VLC (Pin24) Vcc,-1V
RECOMMENDED OPERATING CONDITIONS
V+ Terminal Voltage (Pin16) +6...+11V
CS (Pin18) 0...+11V
Icc (Pin20) 0...3,0mA
VLC (Pin24) 0,55VB...VB,V
Receive Signal (Pin27) 0...250mVrms
Microphone Signal (Pin9) 0...5,0mVrms
Speaker Amp Ground (Pin14) -10...+10mVdc
Ambient Temperature -20...+60C
ELECTRICAL CHARACTERISTICS
SUPPLY VOLTAGE Min Typ Max
V+Supply Current
V+=11V Pin18=0,7V Pin16 - - 9mA
V+=11V Pin18=1,6V - - 800mkA
Vcc Voltage (V+=7.5V) Pin20 4,9Vdc 5,4Vdc 5,9Vdc
Line Regulation (6,5V - 11V) - 65mV 150mV
Output Resistance (Icc=3,0mA) - 6Ohm 20Ohm
Dropout Voltage (V+=5,0V) - 80mV 300mV
VB Voltage (V+=7,5V) Pin21 2,5Vdc 2,9Vdc 3,3Vdc
Output Resistance (IB=1,7mA) - 250Ohm -
ATTENUATORS
Receive Attenuator Gain (@1,0kHz) Pin26,27 Min Typ Max
Rx Mode Pin24=VB Pin27=250mVrms 2,0dB 6,0dB 10dB
Range (Rx to Tx Mode) 40 dB 44dB 40dB
Idle Mode Pin27=250mVrms -20dB -16dB -12dB
RXO Voltage (Rx Mode) 1,8Vdc 2,3Vdc 3,2Vdc
Delta RXO Voltage (Switch from
RX to TX Mode) - - 100mV
RXO Sink Current (Rx Mode) 75mkA - -
RXO Source Current (Rx Mode) 1,0mA - 3,0mA
RXI Input Resistance 3,5k 5,0k 8,0k
Volume Control Range (Rx Att
Gain,Rx Mode,0,6VB Pin24 VB) 24,4dB - 32,5dB
Transmit Attenuator Gain (@1,0kHz) Pin3,4
Tx Mode, Pin3=250mVrms 4,0dB 6,0dB 8,0dB
Range(TxtoRx Mode) 40 dB 44 dB 48dB
Idle Mode,Pin3=250mVrms -16,5dB -13 dB -8,5dB
TXO Voltage (Tx Mode) 1,8Vdc 2,3Vdc 3,2Vdc
Delta TXO Voltage (Switch from
Tx to Rx Mode) - - 100mV
TXO Sink Current (Tx Mode) 74mkA - -
TXO Source Current (Tx Mode) 1,0mA - 3,0mA
TXI Input Resistance 3,5k 5,0k 8,0k
AFC Voltage (Vcc - Pin25 Voltage) Pin20,25
Rx Mode - 150mV -
Rx Mode - 6,0mV -
Idle Mode - 75mV -
SPEAKER AMPLIFIER
Speaker Amp Gain (Pin19=20mVrms) Pin15,19 33dB 34dB 35dB
SKI Input REsistance 15k 22k 37k
SKO Voltage (Pin19=Cap Couple toGND) 2,4Vdc 3,0Vdc 3,6Vdc
SKO High Voltage (Pin19=0,1V;
-100mA load at Pin 15) 5,5Vdc - -
SKO Low Voltage (Pin19=-0,1V;
+100mA load at Pin15) - - 600mV
MICROPHONE AMPLIFIER
Mike Amp Gain (Pin9=10mVrms,1kHz) Pin9,10 32,5dB 34dB 35dB
Mike Amp Input Resistance 6,5k 10k 16k
LOGAMPS
RLO Leakage Current (Pin8=VB+1,0V) - - 2,0mkA
TLO Leakage Current (Pin6=VB+1,0V) - - 2,0mkA
Transmit-Receive Switching Treshold 0,8 - 1,2
(Ratio of ITLI to IRLI - at20mkA - to
switch Tx-Rx Comparator)
TRANSMIT DETECTOR
XDC Voltage Idle Mode Pin23 - 0Vdc -
Tx Mode - 4,0Vdc -
CP2 Current Source Pin12 5,0mkA 10mkA 13mkA
DISTORTION
Rx Mode - RXI to SKO (Pin27= Pin27,15 - 1,5% -
=10mVrms, 1,0kHz)
Tx Mode - MCI to TXO (Pin9= Pin4,9 - 2,0% -
=5,0mVrrms, 1,0kHz)