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LS256BSTN/a30avaiTelephone speech circuit with multifrequency tone generator interface
LS256DSTN/a26avaiTelephone speech circuit with multifrequency tone generator interface


LS256B ,Telephone speech circuit with multifrequency tone generator interfaceELECTRICAL CHARACTERISTICS (refer to the test circuits, S1, S2 in (a),oTamb = – 25 to + 50 C, f = 2 ..
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LS256B-LS256D
TELEPHONE SPEECH CIRCUIT WITH MULTIFREQUENCY TONE GENERATOR INTERFACE
LS256
November 1996
TONE GENERATOR INTERFACE
TELEPHONE SPEECH CIRCUIT WITH MULTIFREQUENCY PRESENTS THE PROPER DC PATHFOR THE
LINE CURRENT. HANDLES THE VOICE SIGNAL, PERFORM-
ING THE 2/4 WIRES INTERFACE AND
CHANGING THE GAIN ON BOTH SENDING
AND RECEIVING AMPLIFIERS TO COMPEN-
SATE FOR LINE ATTENUATION BY SENSING
THELINELENGTHTHROUGHTHELINE CUR-
RENT. ACTS AS LINEAR INTERFACE FORMF, SUP-
PLYINGA STABILIZEDTOTHEDIGITALCHIP
AND DELIVERING TO THE LINE THE MF
TONE GENERATED BY THE DIALER
DESCRIPTION
The LS256isa monolithic integrated circuitin 16-
lead dual in-line and SO20 plastic packagestore-
placethe hybridcircuitin telephoneset.Itworkswith
the same typeof transdurcersfor both transmitter
and receiver (typically piezoceramic capsules, but
DIP16
ORDERING NUMBERS:
LS256B LS256D
the devicecan work alsowith dynamicones).Manyits electrical characteristics canbe controlledby
meansof external componentsto meet different
specifications. additionto the speech operation, the LS256 actsan interfacefor theMF tone signal.
PIN CONNECTIONS (top view)
DIP16
SO20
N.C.
MIC. INPUT
+LINE
MUTING
BIAS ADJ.
DC. REGULATOR
SHUNT REG. BYPASS
LINE CURRENT SENSING
GAIN CONTROL -LINE
INPUT-(REC.AMP.)
INPUT+(REC.AMP.)
RECEIVER OUTPUT
RECEIVER OUTPUT
MFINPUT
VDD
MIC.INPUT
N.C.1
N.C. N.C.
D96TL274
SO20
1/8
BLOCK DIAGRAM (ref.to DIP16)
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit Line Voltage (3ms pulse duration) 22 V Forward Line Current 150 mA Reverse Line Current – 150 mA
Ptot Total Power Dissipationat Tamb =70°C1 W
Top Operating Temperature –45to70 °C
Tstg,Tj Storage and Junction Temperature –65to 150 °C
THERMAL DATA
Symbol Parameter DIP16 SO20 Unit
Rth j-amb Thermal Resistance Junction-ambient Max 80 150 °C/W
LS256
2/8
TEST CIRCUITS (ref.to DIP16)
Figure1. Figure2.
VRO VSOSide tone= ;Gs=VMI VMIV= 0,1V; CMRR
LS256
3/8
Figure3. Figure4.
VROGR= VRI
VMOGMF= VMF
ELECTRICAL CHARACTERISTICS (referto the test circuits, S1, S2in (a),
Tamb=– 25to+ 50oC,f= 200to 3400Hz, unless otherwise specified)
Symbol Parameter Test Conditions Min. Typ. Max. Unit Fig.
SPEECH OPERATION Line Voltage Tamb =25°CIL= 12mA= 20mA= 80mA
3.9 4.7
CMRR Common Mode Rejection f= 1kHz,IL=12to 80mA 50 dB 1 Sending Gain Tamb =25°C,f= 1kHz IL= 52mA
VMI= 2mV IL= 25mA 2
Sending Gain Flatness VMI= 2mV,fref= 1kHz=12to 80mA 1dB 2
Sending Distortion f= 1kHz VSO =1V=16to 80mA VSO= 1.3V
Sending Noise VMI= 0V;IL= 40mA; S1in(b) –68.5 dBmp 2
Microphone Input
Impedance Pin 1-16
VMI= 2mV,IL=12to 80mA 40 kΩ
Sending Lossin MF
Operation
VMI= 2mV IL= 52mAin(b) IL= 25mA
–30 2 Receiving Gain VR1= 0.3V,f= 1kHz, Tamb =25°C= 52mA= 25mA
4.5 3
Receiving Gain Flatness VRI= 0.3V,fref= 1kHz=12to 80mA 1dB 3
Receiving Distortion f= 1kHz IL= 12mA VRO= 1.6V= 12mA VRO= 1.9V= 50mA VRO= 1.8V= 50mA VRO= 2.1V
Receiving Noise VRI= 0V;IL=12to 80mA;S1in(b) 100 μV3
Receiver Output
Impedance Pin 12-13
VRO= 50mV,IL= 40mA 100 Ω
LS256
4/8
ELECTRICAL CHARACTERISTICS (continued)
Symbol Parameter Test Conditions Min. Typ. Max. Unit Fig.
SPEECH OPERATION (continued) Sidetone F= 1kHz, Tamb =25°C,S1in(b)= 52mA= 25mA 2
ZML Line Matching Impedance VRI= 0.3V,f= 1kHz=12to 80mA
500 600 700 Ω
MULTIFREQUENCY SYNTHESIZER INTERFACE
VDD MF Supply Voltage
(standby and operation)=12to 80mA 2.4 2.5 V
IDD MF Supply Current
Standby
Operation=12to 80mA=12to 80mA;S2in(b)
0.5 Amplifier Gain IL=12to 80mA,fMFin= 1kHz
VMFin= 80mV 17 dB 4 DC Input Voltage Level (pin 14) VMFin= 80mV 3VDD V Input Impedance (pin14) VMFin= 80mV 40 kΩ Distortion VMFin= 110mV=12to 80mA 4
Starting Delay Time IL=12to 80mA 5 ms
Muting Threshold Voltage (pin3) Speech Operation 1 V Operation 1.6 V
Muting Standby Current (pin3) IL=12to 80mA –10 μA
Muting Operating Current (pin3) IL=12to 80mA,S2in(b) +10 μA
LS256
5/8
SO20 PACKAGE MECHANICAL DATA
DIM. mm inch
MIN. TYP. MAX. MIN. TYP. MAX. 2.65 0.104 0.1 0.3 0.004 0.012 2.45 0.096 0.35 0.49 0.014 0.019 0.23 0.32 0.009 0.013 0.5 0.020 45° (typ.) 12.6 13.0 0.496 0.512 10 10.65 0.394 0.419 1.27 0.050 11.43 0.450 7.4 7.6 0.291 0.299 0.5 1.27 0.020 0.050 0.75 0.030
S8° (max.)
LS256
6/8
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