LUCL8567AAU-D AGERE [Agere Systems], LUCL8567AAU-D Datasheet - Page 30

• 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 Control—32-Pin PLCC with Power
Control Resistor
The maximum power that may be dissipated in the
SLIC
T
P
Where:
T
and is specified in Table 4.
T
T
avoid driving the SLIC into thermal shutdown.
P
pated on the SLIC to avoid driving the SLIC into ther-
mal shutdown.
the 32-pin PLCC package; it is specified in Table 4 on
page 12.
The approach to choosing the value and rating of R
follows. First use equations 6 and 7 to determine the
maximum allowed power that may be dissipated on the
SLIC without driving the SLIC into thermal shutdown.
Next consider equations 1 and 4. In both equation 1
and 4, pick a value of R
vary V
age to the voltage seen at the minimum expected dc
loop length (100 ). The idea is to use the SLIC power
dissipation value from equation 1, P
the maximum SLIC power dissipation value from equa-
tion 7, P
length. At the same time, using equation 4, try to mini-
mize the power dissipated in R
minimum power rating of the resistor to minimize cost
associated with this resistor. This technique is illus-
trated in the following design example.
30
30
A
TSD
TSD
RISE
SLIC(MAX)
SLIC MAX
JA
is the maximum ambient operating temperature.
is the thermal resistance, junction to ambient of
– T
,
is the thermal protection shutdown temperature
is the maximum allowed SLIC temperature rise to
P
LOOP
SLIC(MAX)
A
SLIC(MAX)
= T
is the maximum allowed power that is dissi-
from the open-circuit (on-hook) state volt-
=
RISE
T
--------------- -
RISE
is given by
, is not exceeded for any value of loop
JA
(continued)
(continued)
PWR
and for this value, or R
PWR
so as to choose the
SLIC
, to ensure that
PWR
PWR
(6)
(7)
,
P
Power Considerations
R
Assume I
current limit is programmed by resistor R
63.4 k , plus a worst-case 15% tolerance that is speci-
fied in Table 5.
|V
2R
the tip and ring lead associated with the L7583 ON
resistance.
V
P
T
T
V
imately 50 V to the voltage at a 100
approximately 5 V.
First, using equations 6 and 7, calculate the maximum
allowed power dissipation in the SLIC.
T
165 C – 85 C = 80 C
P
Given the choice of R
equation 8 must be less than 1.33 W for all loop lengths
(all values of V
R
tion 4.
Inserting values into equation 1:
P
From equation 2, 3, 4, 5
P
2R
Inserting values:
1.33 W < (0.045)(56) + 0.165 W – [(0.045)
2(50 + 18)] –
(V
A
TSD
TSD
ROH
Q
LOOP
SLIC(MAX)
SLIC
SLIC
PWR
SLIC MAX
PWR
JA
BAT
LOOP
= 85 C.
P
P
= 165 mW as nominally specified in Table 4.
–
= 60 C/W per Table 4.
= 136 . This assumes use of 50
– T
| = 56 V.
= 165 C per Table 4.
= 4 V (typical).
Design Example:
should be chosen to minimize P
is varied from the open-circuit voltage of approx-
------------------------------------------------------------------------- -
)(0.045 mA)
P
I
A
LOOP
V
TOTAL
LOOP
= T
BAT
=
=
80 °C
---------------- -
60 °C
RISE
------------------------------------------------------
T
--------------- -
–
= 45 mA. This assumes that a 40 mA
+ P
LOOP
|V
56
RISE
V
R
JA
BAT
ROH
Q
PWR
–
= 1.33 W
in equation 1). At the same time,
– P
| + P
R
4
PWR
–
PWR
–
PROT
V
V
Q
LOO P
chosen, the value of P
LOOP
– (I
– P
LOOP
Lucent Technologies Inc.
2
PWR
2
– V
–
)
2
– P
LOOP
PRW
loop length,
August 1999
LOOP
PROG
PTC in both
Data Sheet
from equa-
2
I
LOOP
set at
SLIC
(6)
(7)
(8)
(9)
in