Datasheet
Data Sheet AD9559
Rev. C | Page 57 of 120
THERMAL PERFORMANCE
Table 33. Thermal Parameters for the 72-Lead LFCSP Package
Symbol Thermal Characteristic Using a JEDEC 51-7 Plus JEDEC 51-5 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) 20.0 °C/W
θ
JMA
Junction-to-ambient thermal resistance, 1.0 m/sec airflow per JEDEC JESD51-6 (moving air) 18.0 °C/W
θ
JMA
Junction-to-ambient thermal resistance, 2.5 m/sec airflow per JEDEC JESD51-6 (moving air) 16.0 °C/W
θ
JB
Junction-to-board thermal resistance, 0.0 m/sec airflow per JEDEC JESD51-8 (still air) 10.7 °C/W
θ
JC
Junction-to-case thermal resistance (die-to-heat sink) per MIL-Std 883, Method 1012.1 1.1 °C/W
Ψ
JT
Junction-to-top-of-package characterization parameter, 0 m/sec airflow per JEDEC JESD51-2 (still air) 0.1 °C/W
Ψ
JT
Junction-to-top-of-package characterization parameter, 1.0 m/sec airflow per JEDEC JESD51-6 (moving air) 0.1 °C/W
Ψ
JT
Junction-to-top-of-package characterization parameter, 2.5 m/sec airflow per JEDEC JESD51-6 (moving air)
0.2
°C/W
1
The exposed pad on the bottom of the package must be soldered to analog 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 if they are similar to those assumed in these calculations.
The AD9559 is specified for a case temperature (T
CASE
). To
ensure that T
CASE
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
× PD)
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 as indicated in Table 33.
PD is the power dissipation (see the Table 3).
Values of θ
JA
are provided for package comparison and PCB
design considerations. θ
JA
can be used for a first-order approx-
imation of T
J
by the equation
T
J
= T
A
+ (θ
JA
× PD)
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.