LUCL8567AAU-D AGERE [Agere Systems], LUCL8567AAU-D Datasheet - Page 28

• Manufacturer Part Number: LUCL8567AAU-D
• Description: SLIC for Peoples Republic of China Applications
• Manufacturer: AGERE [Agere Systems]

L8567 SLIC for
People’s Republic of China Applications
Characteristic Curves
Note: Curve is relevant only to portion of total power dissipation that
Power Control
The total power drawn from the talk battery during an
off-hook state is the product of the battery voltage
times the total dc loop current, plus the SLIC quiescent
power dissipation. Note that during the on-hook state,
the power is simply the SLIC quiescent power.
P
A portion of the total power is dissipated in the sub-
scriber loop, and a portion of the total power is dissi-
pated in the SLIC itself. The loop power is used to drive
the handset and is given by:
P
I
dc loop current will be limited by the SLIC. In the case
of the L8567 SLIC, the dc loop current is determined by
external resistor R
loop resistance (wire resistance and dc handset resis-
tance) plus any protection or other series resistance.
The active or off-hook power dissipated in the SLIC is
simply the difference of the total power drawn from the
talk battery, less the loop power, less the SLIC quies-
cent or on-hook power.
P
28
28
Applications
LOOP
TOTAL(off-hook)
LOOP
SLIC(active)
2000
1500
1000
is actually dissipated on the SLIC.
500
is the dc loop current. In the short dc loops, the
= I
0
20
2
LOOP
= P
40
Figure 25. Power Derating
= V
TOTAL
AMBIENT TEMPERATURE, T
R
BAT
PROG
(continued)
LOOP
60
– P
I
LOOP
. R
LOOP
32 PLCC
80
LOOP
STILL AIR 47 C/W
44 PLCC
+ P
– P
(continued)
100
is the sum of the actual
SLIC(quiescent)
SLIC(on-hook)
120
140
A
( C)
160
12-2825.b (F)
180
If the active power dissipated in the SLIC is too high,
the SLIC temperature will rise above the thermal shut-
down threshold and the SLIC will be driven into a ther-
mal shutdown state. The worst case is under short dc
loops at elevated ambient temperatures. The power
dissipated on the SLIC must be controlled to avoid forc-
ing the SLIC into thermal shutdown during an active
phone conversation.
With the L8567 SLIC, short-loop power dissipation may
be controlled using several user-selectable techniques.
The first involves use of a lower-voltage auxiliary bat-
tery. This will reduce the total short-loop off-hook
power. This has the advantage of not only controlling
the SLIC temperature rise, but also minimizing total
power drawn from the talk battery.
If the user chooses not to provide an auxiliary battery,
the power dissipated by the SLIC must be controlled in
some other manner. With the L8567 SLIC, this may be
done in two ways. One technique involves the use of a
single external power control resistor. This technique
does not minimize total power dissipation; rather it con-
trols the power that it is dissipating through the SLIC
package by removing some power from the SLIC
through the resistor, thus avoiding excess temperature
rise. Because of the higher thermal impedance associ-
ated with the 32-pin PLCC, this technique may be nec-
essary with the 32-pin PLCC package option.
The other technique is simply to choose the 44-pin
PLCC package option. The thermal resistance of the
44-pin PLCC is low enough to ensure, under most con-
ditions, that the thermal shutdown temperature of the
SLIC is not exceeded. Power dissipation calculations
should be made to assess design margin.
For the three configurations discussed above, connec-
tions to the V
in the table below.
Table 17. Power Connections
32 PLCC with auxil-
iary battery
32 PLCC with high-
voltage battery and
power resistor
44 PLCC with high-
voltage battery
Option
BAT1
, V
BAT2
, and PWR nodes are outlined
Connections to Power Mode
V
V
V
V
BAT1
BAT1
BAT1
BAT1
Lucent Technologies Inc.
V
V
V
V
BAT2
BAT2
BAT1
BAT1
August 1999
Data Sheet
through
resistor
control
power
PWR
V
V
V
BAT2
BAT1
BAT1