Pam3101, Application information – Diodes PAM3101 User Manual
Page 12
PAM3101
Document number: DSxxxxx Rev. 2 - 5
12 of 25
October 2012
© Diodes Incorporated
PAM3101
A Product Line of
Diodes Incorporated
Application Information
(cont.)
For example, as
θ
JA
is 250°C/W for the SOT-23 package and 180°C/W for the SOT-89 package based on the standard JEDEC 51-3 for a single-
layer thermal test board, the maximum power dissipation at T
A
+25°C can be calculated by following formula:
W
4
.
0
250
/
C
25
C
125
P
)
MAX
(
D
SOT-23
W
55
.
0
180
/
C
25
C
125
P
)
MAX
(
D
SOT-89
It is also useful to calculate the junction temperature of the PAM3101 under a set of specific conditions. Suppose the input voltage V
IN
= 3.3V,
the output current I
O
= 300mA and the case temperature T
A
= +40°C measured by a thermalcouple during operation, the power dissipation for
the V
O
= 2.8V version of the PAM3101 can be calculated as:
mW
150
A
70
*
V
3
.
3
mA
300
*
V
8
.
2
V
3
.
3
P
D
And the junction temperature, T
J
can be calculated as follows:
T
J
= T
A
+ P
D
*
θ
JA
T
J
= 40°C +0.15W*250°C/W
= 40°C +37.5°C
= 77.5°C J(MAX) = +125°C For this application, T J is lower than the absolute maximum operating junction temperature, +125°C, so it is safe to use the PAM3101 in this configuration.