Datasheet

AD9553
Rev. A | Page 29 of 44
APPLICATIONS INFORMATION
THERMAL PERFORMANCE
The AD9553 is specified for case temperature (T
CASE
). To ensure
that T
CASE
is not exceeded, use an airflow source. Use the following
equation to determine the junction temperature on the applica-
tion printed circuit board (PCB):
T
J
= T
CASE
+ (Ψ
JT
× P
D
)
where:
T
J
is the junction temperature (°C).
T
CASE
is the case temperature (°C) measured by the customer
at the top center of the package.
Ψ
JT
is the value indicated in Table 23.
P
D
is the power dissipation (see Table 1 for the power consumption
parameters).
Valu es of θ
JA
are provided for package comparison and PCB design
considerations. θ
JA
can be used for a first-order approximation
of T
J
using the following equation:
T
J
= T
A
+ (θ
JA
× P
D
)
where T
A
is the ambient temperature (°C).
Valu es of θ
JC
are provided for package comparison and PCB
design considerations when an external heat sink is required.
Valu es of θ
JB
are provided for package comparison and PCB
design considerations.
Table 23. Thermal Parameters for the 32-Lead LFCSP Package
Symbol Description Value
1
Unit
θ
JA
Junction-to-ambient thermal resistance, 0 m/sec airflow per JEDEC JESD51-2 (still air) 41.6 °C/W
θ
JMA
Junction-to-ambient thermal resistance, 1.0 m/sec airflow per JEDEC JESD51-6 (moving air) 36.4 °C/W
θ
JMA
Junction-to-ambient thermal resistance, 2.5 m/sec airflow per JEDEC JESD51-6 (moving air) 32.6 °C/W
θ
JB
Junction-to-board thermal resistance, 0 m/sec airflow per JEDEC JESD51-8 (still air) 24.2 °C/W
Ψ
JB
Junction-to-board characterization parameter, 0 m/sec airflow per JEDEC JESD51-6 (still air) 22.9 °C/W
θ
JC
Junction-to-case thermal resistance 4.8 °C/W
Ψ
JT
Junction-to-top-of-package characterization parameter, 0 m/sec airflow per JEDEC JESD51-2 (still air) 0.5 °C/W
1
Results are from simulations. The PCB is a JEDEC multilayer type. Thermal performance for actual applications requires careful inspection of the conditions in the
application to determine whether they are similar to those assumed in these calculations.