LS285 ,Telephone Speech Circuitsdn,, tifiiliiJl',!illl!lfiil!ll _ Lti285
TELEPHONE SPEECH CIRCUITS
. 2/4 WIRE INTERFACE
I OP ..
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" mneheat taetmmnee LS356
TELEPHONE SPEECH CIRCUIT WITH MULTIFREQUENCY
TON ..
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LS285
Telephone Speech Circuits
/iio7i,r ggggggmkflwgvméflgmqg . Lti285
TELEPHONE SPEECH CIRCUITS
n 2/4 WIRE INTERFACE
u OPERATES DOWN TO 4 mA
I: 3.5 Vpp DYNAMIC IN SENDING AT 25 mA
DESCRIPTION
The LS285 is monolithic integrated circuits for re-
placement of the hybrid circuit (2-4 wire interface) in
conventional telephones interfacing the two
transducers to the line and providing a controlled
amou nt of sidetone.
The same type of transducer can be used for both DIP14
transmitter and receiver, usually a 350 Q dynamic
By sensing the line current, LS285 adjusts the gain
in both directionsto compensate for line attenuation. .
Output impedance can be matched to the line, inde- ORDERING NUMBER : LS285AB1
pendent of transducer impedance.
The LS285 is packaged in a 14 lead dual in-line
plastic package.
PIN CONNECTION/top view)
Recewea f 1 u. RECEIVER
OUTPUT OUTPUT
LINEIMP. .v
ADJUST. [2 13 il L
.vL [3 12 , INPUT REC,
0c REGULAIOR[ a ll INPUT REC.
BIAS f ti 10 ] MICJNPUT
AC LOOP f t) 9 l MICJNPUI
OPENING
NC I 7 8 J NC
March 1993 1/8
© 'niiHi3' UUSBHHB Mi'il III
BLOCK DIAGRAM
REGUL ATDR
OUIPU t
STA GE
. 5-3791"
________________ l
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
VL Line Voltage (3 ms pulse duration) 22 V
IL Forward Current 120 mA
IL Reverse Current - 150 mA
Ptot Total Power Dissipation at Tamb = 70 °C 1 W
Tstg Storage and Junction Temperature - 55 to 150 oc
Top Operating Temperature - 40 to 70 °C
THERMAL DATA
Symbol Parameter Value Unit
Rmrams Thermal Resistance Junction-ambient Max<0> 80 °C/W
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