LUCL9310AP-D AGERE [Agere Systems], LUCL9310AP-D Datasheet - Page 33

• Manufacturer Part Number: LUCL9310AP-D
• Description: Line Interface and Line Access Circuit Full-Feature SLIC,Ringing Relay,and Test Access Device
• Manufacturer: AGERE [Agere Systems]

July 2001
Applications
dc Characteristics
Automatic Battery Switch
Use of the automatic battery switch controls power dis-
sipation by automatically switching to the lower-voltage
auxiliary battery under short dc loop conditions, thus
reducing the short-loop power that is generated. This
has the advantage of not only controlling device tem-
perature rise, but reducing overall power dissipation.
The switch will automatically apply the appropriate bat-
tery to support the dc loop. No logic control is needed
to control the switch. Switching is quiet, and the dc loop
current will not be interrupted when switching between
batteries. The lower-voltage auxiliary battery is con-
nected to the V
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 12.
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
Agere Systems Inc.
BAT2
LOOP
protection resistance, and dc feed resistance
[100
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
LIM
BAT2
BAT2
–
, add:
3.0
(continued)
/PRW package pin.
BAT1
+ 1 V + (50
– 2R
.
(continued)
P
– R
dc
x I
LOOP
loop, 30
Full-Feature SLIC, Ringing Relay, and Test Access Device
OVH
), at least
OVH
= 0):
= 0).
pro-
BAT2
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.
Figure 12. L9310 Loop/Battery Current (with
BAT1
BAT2
= 1.39 mA + 2.5 mA + 0.02 x (42 mA – 2.5 mA) =
= (0.98) x 42 mA = 38.71 mA
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
0
Battery Switch) vs. Loop Resistance
BAT1
I
BAT2
200
and V
I
LOOPdc
BAT2
BAT2
400
R
. Over a large number of
currents will be:
LOOP
BAT
I
( )
BAT1
= –48 V)
600
to 640 , the
800
12-3470a (F)
1000
33