LUCL9312AP-D AGERE [Agere Systems], LUCL9312AP-D Datasheet - Page 24

• 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
Automatic Battery Switch (continued)
The equation governing the switch point is as follows:
R
A graph showing loop and battery current versus loop
resistance with use of the battery switch is shown in
Figure 11.
The V
power dissipation is minimized. When the voltage at
pin PR equals V
98% of the loop current minus 2.5 mA flows into V
and 2.5 mA + 2% of the loop current plus quiescent
current flows into V
To choose V
1. Maximum tip overhead voltage (2 V for V
2. Maximum loop voltage (maximum loop resistance,
3. 1 V for the soft switch.
Thus, for a 40 mA current limit, 640
tection resistors, and 3.17 dBm signal (V
V
Then, for any loop resistance from 0
worst-case V
I
4.68 mA
I
Total max power = 1.641 W (V
Note that to minimize power statistically, this may not
be the best choice for V
lines, power is minimized according to the statistical
distribution of loop resistance.
24
BAT1
BAT2
BAT2
LOOP
protection resistance, and dc feed resistance
[100
= 1.39 mA + 2.5 mA + 0.02 x (42 mA – 2.5 mA) =
= (0.98) x 42 mA = 38.71 mA
BAT2
= –(2 + 0.042 x (100 + 60 + 640) + 1) = –36.6 V
=
-----------------------------------
V
] times the maximum loop current limit).
voltage must be chosen properly so that the
BAT2
BAT2
I
BAT1
LIM
BAT2
–
, add:
and V
3.0
(continued)
BAT1
+ 1 V + (50
– 2R
.
(continued)
BAT2
BAT2
P
. Over a large number of
currents will be:
– R
BAT
dc
= –48 V)
x I
LOOP
loop, 30
to 640 , the
OVH
), at least
OVH
= 0):
= 0).
pro-
BAT2
Figure 11. L9312 Loop/Battery Current (with Battery
Power Control Resistor
Device temperature rise may be controlled with use of
a single battery voltage by use of a power control resis-
tor. This technique will reduce power dissipation on the
chip, by sharing the total power not dissipated in the
loop between the L9312 and the power control resistor.
It does not, however, reduce the total power con-
sumed, as does use of the auxiliary battery. The power
control resistor is connected from the primary battery to
the V
The magnitude of the power control resistor must be
low enough to ensure that sufficient power is dissipated
on the resistor to ensure the L9312 does not exceed its
thermal shutdown temperature. At the same time, the
more power that is dissipated by the power control
resistor, the higher the resistor’s power rating must be,
and thus, the more costly the resistor. The following
equations are used to optimize the choice (magnitude
and power rating) of the power control resistor.
0.030
0.028
0.026
0.024
0.022
0.020
0.018
0.016
0.014
0.012
0.010
0.008
0.006
0.004
0.002
0.000
BAT2
/PWR node of the device.
0
Switch) vs. Loop Resistance
I
BAT2
200
I
LOOPdc
400
R
LOOP
( )
I
BAT1
600
Agere Systems Inc.
800
July 2001
12-3470a (F)
1000