Data Sheet
September 2001
Full-Feature SLIC and Ringing Relay for TR-57 Applications
L9313 Line Interface and Line Access Circuit
28
Agere Systems Inc.
Applications
(continued)
dc Characteristics
(continued)
Battery Feed
(continued)
As illustrated in Figure 12, as loop length decreases,
the tip to ground voltage will decrease with a slope cor-
responding to one-half the internal dc feed resistance
of the SLIC (typical 75
). The ring to ground voltage
will also decrease with a slope corresponding to one-
half the internal dc feed resistance of the SLIC, until the
SLIC reaches the current-limit region of operation. At
that point, the slope of the ring to ground voltage will
increase to the sum of one half the internal dc feed
resistance plus approximately 10 k
.
The dc feed characteristic can be described by:
I
LOOP
=
V
T/R
=
where:
I
LOOP
= dc loop current.
V
T/R
= dc loop voltage.
V
BAT
= battery voltage magnitude.
V
OH
= overhead voltage.
R
LOOP
= loop resistance, including wire and handset
resistance.
R
P
= protection resistance.
R
dc
= SLIC internal dc feed resistance.
12-3050.g (F)
Notes:
V
BAT1
= –48 V.
V
BAT2
= –24 V.
I
LIM
= 40 mA (R
PROG
= 66.5 k
).
Figure 13. L9313 Loop Current vs. Loop Voltage
Refer to Figure 12 and Figure 13 in this section and to Fig-
ure 11 in the Automatic Battery Switch section.
Starting from the on-hook condition and going through
to a short circuit, the curve passes through two regions:
Region 1: on-hook and low loop currents: the slope cor-
responds to the dc feed resistance of the SLIC (plus
any series resistance). The open-circuit voltage is the
battery voltage less the overhead voltage of the device.
Region 2: current limit: the dc current is limited to a
value determined by V
PROG
. This region of the dc tem-
plate has a high resistance (10 k
).
Notice that the I-V curve is uninterrupted when the
power is shifted from the high-voltage battery to the
low-voltage battery (if auxiliary battery option is used).
This is shown in Figure 11 in the Automatic Battery
Switch section.
Battery Reversal Rate
The rate of battery reverse is controlled or ramped by
capacitors FB1 and FB2. A chart showing FB1/FB2 val-
ues versus typical ramp time is given below. Leave
FB1 and FB2 open if it is not desired to ramp the rate of
battery reversal.
Table 15. FB1/FB2 Values vs. Typical
Ramp Time
* Typical recommended value for C
FB1
and C
FB2
is less
than 0.033
μ
F.
Longitudinal to Metallic Balance
Longitudinal to metallic balance at PT/PR is specified in
the Electrical Characteristics section of this data sheet.
BAT
V
OH
–
R
LOOP
2R
P
R
dc
+
+
----------V
BAT
R
LOOP
V
OH
2R
P
+
–
----V
)
R
LOOP
R
dc
+
L
0
5
10
25
0
20
30
40
50
LOOP VOLTAGE (V)
15
20
10
1
R
dc
30
45
35
40
1
10 k
C
FB1
/C
FB2
*
0.01
μ
F
0.1
μ
F
0.22
μ
F
0.47
μ
F
1.0
μ
F
1.22
μ
F
1.3
μ
F
1.4
μ
F
1.6
μ
F
Transition Time
20 ms
220 ms
440 ms
900 ms
1.8 s
2.25 s
2.5 s
2.7 s
3.2 s