LUCL9311AP-D AGERE [Agere Systems], LUCL9311AP-D Datasheet - Page 29

• Manufacturer Part Number: LUCL9311AP-D
• Description: Line Interface and Line Access Circuit Full-Feature SLIC with High Longitudinal Balance, Ringing Relay,and GR-909 Test Access
• 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
Then, for any loop resistance from 0
worst-case V
I
4.68 mA
I
Total max power = 1.641 W (V
Agere Systems Inc.
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
BAT2
–
, add:
and V
3.0
(continued)
/PRW package pin.
BAT1
+ 1 V + (50
– 2R
.
(continued)
BAT2
P
currents will be:
– R
BAT
dc
= –48 V)
x I
LOOP
loop, 30
to 640 , the
OVH
), at least
OVH
= 0):
= 0).
pro-
BAT2
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. L9311 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 L9311 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
Ringing Relay, and GR-909 Test Access
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
BAT2
400
R
. Over a large number of
LOOP
I
( )
BAT1
600
800
12-3470a (F)
1000
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