Datasheet

Data Sheet AD9523
Rev. C | Page 39 of 60
The second step is to multiply the power dissipated by the thermal
impedance to determine the maximum power gradient. For this
example, a thermal impedance of
θ
JA
= 20.1°C/W was used.
Example 1
(868 mW × 20.1°C/W) = 17.4°C
With an ambient temperature of 85°C, the junction temperature is
T
J
= 85°C + 17.4°C = 102°C
This junction temperature is below the maximum allowable.
Example 2
(2500 mW × 20.1°C/W) = 50.2°C
With an ambient temperature of 85°C, the junction temperature is
T
J
= 85°C + 50°C = 135°C
This junction temperature is above the maximum allowable. To
operate in the condition of Example 2, the ambient temperature
must be lowered to 65°C.
THERMALLY ENHANCED PACKAGE MOUNTING
GUIDELINES
Refer to the AN-772 Application Note, A Design and
Manufacturing Guide for the Lead Frame Chip Scale Package
(LFCSP), for more information about mounting devices with
an exposed paddle.