LUCL9219AAR-D AGERE [Agere Systems], LUCL9219AAR-D Datasheet - Page 19

• Manufacturer Part Number: LUCL9219AAR-D
• Description: Low-Cost Line Interface with Reverse Battery and Dual Current Limit
• Manufacturer: AGERE [Agere Systems]

Data Sheet
November 2001
Agere Systems Inc.
Applications
dc Applications
Battery Feed
The dc feed characteristic can be described by:
where:
I
V
|
V
R
R
R
Notes:
V
I
R
L
LIM
V
BAT
dc1
T/R
OH
L
P
dc
= dc loop current.
BAT
= loop resistance, not including protection resistors.
= protection resistor value.
= 22 mA.
= SLIC internal dc feed resistance.
= 80 .
= –48 V.
= overhead voltage. This is the difference between
= dc loop voltage.
|
Figure 13. Loop Current vs. Loop Voltage
the battery voltage and the open loop tip/ring
voltage.
50
40
30
20
10
= battery voltage magnitude.
0
0
I
LIM
V
TESTED
T/R
I
10
L
(continued)
=
12.5 k
=
-------------------------------------------- -
1
--------------------------------- -
R
LOOP VOLTAGE (V)
V
R
L
V
B A T
20
L
+
B AT
+
2R
2R
–
–
P
V
P
V
+
O H
+
O H
R
30
R
dc
I
LIM
dc
R
ONSET
–1
R
dc1
L
40
12-3050 (F).i
50
with Reverse Battery and Dual Current Limit
Starting from the on-hook condition and going through
to a short circuit, the curve passes through the follow-
ing two regions:
Region 1: On-hook and low loop currents. The slope
Region 2: Current limit. The dc current is limited to a
Current Limit
With the logic inputs set to 11 (a low current limit active
state), current limit with a 100
lowing:
Via the logic table, the current limit can be increased a
nominal 42% from the value set by the R
The relationship between low current limit and high
current limit is as follows:
Overhead Voltage
In order to drive an on-hook ac signal, the SLIC must
set up the tip and ring voltage to a value less than the
battery voltage. The amount that the open loop voltage
is decreased relative to the battery is referred to as the
overhead voltage and is expressed as the following
equation:
Without this buffer voltage, amplifier saturation will
occur and the signal will be clipped. The L9219 is auto-
matically set at the factory to allow undistorted on-hook
transmission of a 3.14 dBm signal into a 900
impedance.
0.637 R
corresponds to the dc resistance of the
SLIC, R
circuit voltage is the battery voltage minus
the overhead voltage of the device, V
(default is 6.5 V typical). These values are
suitable for most applications, but can be
adjusted if needed. For more information,
see the sections entitled Adjusting dc Feed
Resistance and Adjusting Overhead Voltage.
starting value determined by external resis-
tor R
source, and the gain from tip/ring to pin
VITR.
L9219A/G Low-Cost Line Interface
V
PROG
OH
PROG
dc1
---------------------------------- -
I
I
= |V
LIMIT
LIMIT
, the logic table, an internal current
(default is 70
(k ) + 2 mA = I
BAT
High
Low
| – (V
PT
= 0.7
load is given by the fol-
– V
typical). The open
LIM
PR
)
x (mA)
PROG
resistor.
OH
loop
19