Datasheet
Data Sheet AD9552
Rev. E | Page 19 of 32
APPLICATIONS INFORMATION
THERMAL PERFORMANCE
Table 13. Thermal Parameters for the 32-Lead LFCSP Package
Symbol Thermal Characteristic Using a JEDEC51-7 Plus JEDEC51-5 2S2P Test Board
1
Value
2
Unit
θ
JA
Junction-to-ambient thermal resistance, 0.0 m/sec airflow per JEDEC JESD51-2 (still air) 40.5 °C/W
θ
JMA
Junction-to-ambient thermal resistance, 1.0 m/sec airflow per JEDEC JESD51-6 (moving air) 35.4 °C/W
θ
JMA
Junction-to-ambient thermal resistance, 2.5 m/sec airflow per JEDEC JESD51-6 (moving air) 31.8 °C/W
θ
JB
Junction-to-board thermal resistance, 1.0 m/sec airflow per JEDEC JESD51-8 (moving air) 23.3 °C/W
θ
JC
Junction-to-case thermal resistance (die-to-heat sink) per MIL-Std 883, Method 1012.1 4.2 °C/W
Ψ
JT
Junction-to-top-of-package characterization parameter, 0 m/sec airflow per JEDEC JESD51-2 (still air) 0.4 °C/W
1
The exposed pad on the bottom of the package must be soldered to ground to achieve the specified thermal performance.
2
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.
The AD9552 is specified for an ambient temperature (T
A
). To
ensure that T
A
is not exceeded, an airflow source can be used.
Use the following equation to determine the junction tempera-
ture on the application 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 13.
P
D
is the power dissipation (see the Specifications section).
Values 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).
Values of θ
JC
are provided for package comparison and PCB
design considerations when an external heat sink is required.
Values of θ
JB
are provided for package comparison and PCB
design considerations.