Datasheet

Data Sheet ADP2105/ADP2106/ADP2107
Rev. D | Page 23 of 36
For example, in an application where the ADP2107(1.8 V) is
used with an input voltage of 3.6 V, a load current of 2 A, and a
maximum ambient temperature of 85°C, at a load current of 2 A,
the most significant contributor of power dissipation in the dc-to-
dc converter package is the conduction loss of the power switches.
Using the graph of switch on resistance vs. temperature (see
Figure 30), as well as the equation of power loss given in the
Power Switch Conduction Losses section, the power dissipation
in the package can be calculated by the following:
P
SW − COND
= [R
DS(ON) − P
× D + R
DS(ON) − N
× (1 − D)] × I
OUT
2
=
[109 mΩ × 0.5 + 90 mΩ × 0.5] × (2 A)
2
≈ 400 mW
The θ
JA
for the LFCSP_VQ package is 40°C/W, as shown in
Table 3. Therefore, the rise in temperature of the package due to
power dissipation is
T
R
= θ
JA
× P
D
= 40°C/W × 0.40 W = 16°C
The junction temperature of the converter is
T
J
= T
A
+ T
R
= 85°C + 16°C = 101°C
Because the junction temperature of the converter is below the
maximum junction temperature of 125°C, this application operates
reliably from a thermal point of view.