Datasheet

ADP7182 Data Sheet
Rev. C | Page 26 of 28
Thermal Characterization Parameter, Ψ
JB
When the board temperature is known, use the thermal
characterization parameter, Ψ
JB
, to estimate the junction
temperature rise (see Figure 93 and Figure 94). Maximum
junction temperature (T
J
) is calculated from the board temperature
(T
B
) and power dissipation (P
D
) using the following formula:
T
J
= T
B
+ (P
D
× Ψ
JB
) (6)
The typical value of Ψ
JB
is 18.2°C/W for the 8-lead LFCSP package
and 43°C/W for the 5 lead TSOT package.
140
120
100
80
60
40
20
0
0
75
6
4
32
1
JUNCTION TEMPERATURE, T
J
(°C)
TOTAL POWER DISSIPATION (W)
T
B
= 25°C
T
B
= 50°C
T
B
= 85°C
T
J
MAX
10703-093
Figure 93. Junction Temperature vs. Total Power Dissipation for the
8-Lead LFCSP, T
A
= 85°C
140
120
100
80
60
40
20
0
0 75 64321
JUNCTION TEMPERATURE, T
J
(°C)
TOTAL POWER DISSIPATION (W)
T
B
= 25°C
T
B
= 50°C
T
B
= 85°C
T
J
MAX
10703-094
Figure 94. Junction Temperature vs. Total Power Dissipation for the
5-Lead TSOT, T
A
= 85°C
PCB LAYOUT CONSIDERATIONS
Place the input capacitor as close as possible to the VIN and GND
pins. Place the output capacitor as close as possible to the VOUT
and GND pins. Use of 1206 or 0805 size capacitors and resistors
achieves the smallest possible footprint solution on boards where
area is limited.
10703-095
Figure 95. Example of the 8-Lead LFCSP PCB Layout
10703-096
Figure 96. Example of the 5-Lead TSOT PCB Layout