LUCL8567AAU-D AGERE [Agere Systems], LUCL8567AAU-D Datasheet - Page 32

• 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
Applications
Power Considerations
Table 21. R
Table 22. R
Table 23. R
32
32
P
P
P
1.682555
1.558691
1.423464
1.276873
1.118918
0.768918
0.576873
0.373464
0.158691
1.228323
1.195964
1.141959
0.969016
0.850076
0.709492
0.547262
0.363388
0.157868
1.127662
1.115581
1.079576
1.019648
0.935796
0.828021
0.696322
0.361155
0.157686
1.06631
0.9496
0.5407
SLIC
SLIC
SLIC
(W)
(W)
(W)
PWR
PWR
PWR
V
V
V
= 4400
= 2310
= 2090
LOOP
LOOP
LOOP
(continued)
10
15
20
25
30
35
40
45
50
10
15
20
25
30
35
40
45
50
10
15
20
25
30
35
40
45
50
5
5
5
(V)
(V)
(V)
(R
(R
PWR
PWR
(continued)
R
R
R
PWR
PWR
PWR
4400
4400
4400
4400
4400
4400
4400
4400
4400
4400
2310
2310
2310
2310
2310
2310
2310
2310
2310
2310
2090
2090
2090
2090
2090
2090
2090
2090
2090
2090
= 2200
= 2200
( )
( )
( )
P
P
P
0.502045
0.400909
0.311136
0.232727
0.165682
0.065682
0.032727
0.011136
0.000909
0.956277
0.763636
0.592641
0.315584
0.209524
0.125108
0.062338
0.021212
0.001732
1.056938
0.844019
0.655024
0.489952
0.348804
0.231579
0.138278
0.023445
0.001914
+ 5%)
0.44329
– 5%)
PWR
PWR
PWR
0.0689
0.11
(W)
(W)
(W)
Power Control—44-Pin PLCC Package
With the 44-pin PLCC, the thermal impedance of the
package is probably enough to ensure the SLIC ther-
mal shutdown temperature is not exceeded. Power cal-
culations, as illustrated below, should be made to
ensure design margin.
The still-air thermal resistance of the 44-pin PLCC is
47 °C/W; however, this number implies zero airflow as if
the L8567 were totally enclosed in a box. A more realis-
tic number would be 43 °C/W. This is an experimental
number that represents a thermal impedance with no
forced airflow (i.e., from a muffin fan), but from the nat-
ural airflow as seen in a typical switch cabinet.
The SLIC will enter the thermal shutdown state at typi-
cally 165 °C. The thermal shutdown design should
ensure that the SLIC temperature does not reach
165 °C under normal operating conditions.
Assume a maximum ambient operating temperature of
85 °C, a maximum current limit of 45 mA, and a maxi-
mum battery of –52 V. Further, assume a (worst case)
minimum dc loop of 100
resistors are used at both tip and ring.
1. T
2. Allowed thermal rise = package thermal
Thus, if the total power dissipated in the SLIC is less
than 1.9 W, it will not enter the thermal shutdown state.
Total SLIC power is calculated as:
For the L8567, SLIC quiescent power (P
mated at 0.167 W. Thus,
The power dissipated in the SLIC is the total power dis-
sipation less the power that is dissipated in the loop.
Thus, in this example, the thermal design ensures that
the SLIC will not enter the thermal shutdown state.
impedance
80 °C = 43 °C/W
SLIC power dissipation (P
Total P
Total P
Total P
Total P
SLIC P
Loop power = (I
Loop power = (45 mA)
Loop power = 0.61 W
SLIC power = 2.507 W – 0.61 W
SLIC power = 1.897 W < 1.9 W
165 °C – 85 °C = 80 °C
current limit + SLIC quiescent power.
TSD
– T
D
D
D
D
D
A(max)
= Maximum battery
= (–52 V
= 2.34 W + 0.167 W
= 2.507 W
= Total power – Loop power
•
SLIC power dissipation.
= allowed thermal rise.
LIM
•
•
)
SLIC power dissipation
2
45 mA) + 0.167 W
•
2
(R
and that 100
•
dcLOOP
(100
D
Lucent Technologies Inc.
) = 1.9 W
•
Maximum
min + 2R
+ 200
August 1999
Q
Data Sheet
) is approxi-
protection
P
)
)