
FUNCTIONAL DESCRIPTION
L3000S - HIGHVOLTAGECIRCUIT
The L3000S line interface provides battery feed
for telephone lines and ringing injection. Both
these operationsare done in Balance Mode. This
is very important in order to avoid the generation
of common mode signals in particular during the
pulse dialling operation of the telephone set con-
nected to the SLIC. The IC contains a state de-
coder that under externalcontrol can force the fol-
lowing
operational
conversationand ringing.
In addition Power down mode can be forced con-
necting the bias current resistor to V
DD
or leaving
it open.
Two pins, I
L
and I
T
, carry out the information con-
cerning line status which is detected by sensing
the line currentinto the output stage.
The L3000S amplifies both the AC and DC signals
enteringat pin6 (VIN) by a factorequalto 40.
Separate groundsare provided:
- Analog ground as reference for analog sig-
nals
- Battery ground as a reference for the output
stages
The two ground should be shorted together at a
low impedancepoint.
modes
:
stand-by,
L3092 - LOWVOLTAGE CIRCUIT
The L3092 Low Voltage Control Unit controls the
L3000S line interface module providing set up
data to set line feed characteristics and to inject
ringing. An on chip digital parallel interface allows
a
microprocessor
or
COMBO as the TS5070 to control all the opera-
tions.
L3092 defines working states of Line Interface
Circuit and also informs the card controller about
line status.
a
second
generation
L3000S WORKING STATES
In order to carry out the different possible opera-
tions, the L3000S has several different working
states. Each state is defined by the voltage re-
spectively applied by pin 12 and 13 of L3092 to
the pins 12 and 11 of L3000S.
Three different voltage levels (–3, 0, +3) are avail-
able at eachconnection,so definingnine possible
statesas listedin tab. 1.
Appropriate combinations of two pins define four
of the five possible L3000S working states that
are:
a) Stand-by(SBY)
b) Conversation(CVS)
FUNCTIONAL DIAGRAM
L3000S
L3000S - L3092
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