Ap1184, Functional descriptions – Diodes AP1184 User Manual
Page 7
AP1184
4A ULTRA LOW DROPOUT POSITIVE ADJUSTABLE OR
FIXED-MODE REGULATOR
AP1184 Rev. 5
7 of 12
SEPTEMBER 2008
www.diodes.com
©
Diodes Incorporated
Functional Descriptions
(Continued)
Assuming, the following conditions:
V
out
= 2.5V
V
in
= 3.3V
V
ctrl
= 5V
I
out
= 2A DC Avg.
Calculate the maximum power dissipation using the following equation:
P
d
= I
out
* ( V
in
- V
out
) + ( I
out
/60) * ( V
ctrl
- V
out
)
P
d
= 2 * (3.3-2.5) + (2/60) * (5-2.5) = 1.68W
Using table below select the proper package and the amount of copper board needed.
Package
Copper Area
θ
JA
(
o
C/W)
Max Pd (T
A
= 25
o
C)
Max Pd (T
A
= 45
o
C)
TO263-5L Pad
Size-1.4”X1.4”
25-45
2.4W-4.4W
2.0W-3.6W
Notes: 6. Above table is based on the maximum junction temperature of 135
o
C.
As shown in the above table, any of the two packages will do the job.