LUCL9312AP-D AGERE [Agere Systems], LUCL9312AP-D Datasheet - Page 26

• Manufacturer Part Number: LUCL9312AP-D
• Description: Line Interface and Line Access Circuit Forward Battery SLIC and Ringing Relay for TR-57 Applications
• Manufacturer: AGERE [Agere Systems]

Forward Battery SLIC and Ringing Relay for TR-57 Applications
Applications
dc Characteristics
dc Loop Current Limit
In the active modes, dc current limit is programmable
via an applied voltage source at the device’s V
control input. The voltage source may be an external
voltage source or derived via a resistor divider network
from the V
source. A programmable external voltage source may
be used to provide software control of the loop current
limit. The loop current limit (I
voltage by:
I
Note that the overall current-limit accuracy achieved
will not only be affected by the specified accuracy of
the internal SLIC current-limit circuit (accuracy associ-
ated with the 50 term), but also by the accuracy of the
voltage source and the accuracy of any external resis-
tor divider network used and voltage offsets due to the
specified input bias current. If a resistor divider from
V
more accurate result due to a lower offset associated
with the input bias current; however, lower value resis-
tors will also draw more power from V
the two resistors in the resistor divider should be
between 75 k
accuracies are specified in Table 6.
The above equation describes the active mode steady-
state current-limit response. There will be a transient
response of the current-limit circuit (with the device in
the active mode) upon an on- to off-hook transition.
Typical active mode transient current-limit response is
given in Table 14.
Table 14. Typical Active Mode On- to Off-Hook Tip/
26
LIM
dc Loop Current:
dc Loop Current:
dc Loop Current:
REF
Active Mode
R
Active Mode
R
Active Mode
R
(mA) = 50 x V
LOOP
Transition t < 5 ms
LOOP
Transition t < 50 ms
LOOP
Transition t < 300 ms
is used, a lower magnitude resistor will give a
= 100
= 100
= 100
Ring Current-Limit Transient Response
REF
Parameter
SLIC output or an external voltage
and 200 k . Offset at V
PROG
On- to Off-hook
On- to Off-hook
On- to Off-hook
(continued)
(V)
(continued)
LIM
) is related to the V
REF
I
I
LIM
LIM
PROG
Value
. The sum of
I
LIM
+ 60
+ 20
and V
PROG
Unit
PROG
mA
mA
mA
REF
The current limit with the SLIC set in an active mode
will be different from the current limit with the SLIC set
in the scan mode. This is due to differences in the scan
clamp circuit versus the active tip/ring drive amplifiers.
The scan mode current limit is fixed and is a function of
the internal design of the scan clamp circuit. The
steady-state scan mode current limit will be a typical
40 mA to 50 mA and may, over temperature and pro-
cess, vary typically from 30 mA to 110 mA. The scan
clamp current limit will typically settle to its steady-state
value within 300 ms.
Loop Range
The dc loop range is calculated using:
R
V
loop range. The loop resistance value where the device
automatically switches to V
Automatic Battery Switch section of this data sheet.
Battery Feed
The L9312 operates in a dc unbalanced mode. In the
forward active state, under open circuit (on-hook) con-
ditions, with the default overhead chosen, the tip to ring
voltage will be a nominal 5.5 V less than the battery.
This is the overhead voltage. The tip and ring overhead
is achieved by biasing ring a nominal 3.5 V above bat-
tery and by biasing tip a nominal 2.0 V below ground.
During off-hook conditions, some dc resistance will be
applied to the subscriber loop as a function of the phys-
ical loop length, protection, and telephone handset. As
the dc resistance decreases from infinity (on-hook) to
some finite value (off-hook), the tip to ring voltage will
decrease as shown in Figure 12.
VRING TO GND
BAT1
L
VTIP TO GND
=
is used because we are calculating the maximum
----------------------------------
V
V
BAT
BAT
I
LOOP
Figure 12. Tip/Ring Voltage
–
V
OH
(1/2)R
(1/2)R
BEGIN CURRENT LIMITING
dc
dc
– 2R
P
BAT2
– R
dc
is calculated in the
DECREASING LOOP LENGTH
Agere Systems Inc.
July 2001
(1/2)R
12-3431a (F)
dc
+ R
LIM