AD9551SLASHPCBZ datasheet(25/40 Pages) AD

25 / 40 page

AD9551

Rev. B | Page 25 of 40

APPLICATIONS INFORMATION

THERMAL PERFORMANCE

Table 18. Thermal Parameters for the 40-Lead LFCSP Package

Symbol

Thermal Characteristic Using a JEDEC51-7 Plus JEDEC51-5 2S2P Test Board1

Value2

Unit

θJA

Junction-to-ambient thermal resistance, 0.0 m/sec airflow per JEDEC JESD51-2 (still air)

°C/W

θJMA

Junction-to-ambient thermal resistance, 1.0 m/sec airflow per JEDEC JESD51-6 (moving air)

°C/W

θJMA

Junction-to-ambient thermal resistance, 2.5 m/sec airflow per JEDEC JESD51-6 (moving air)

°C/W

θJB

Junction-to-board thermal resistance, 1.0 m/sec airflow per JEDEC JESD51-8 (moving air)

°C/W

θJC

Junction-to-case thermal resistance (die-to-heat sink) per MIL-Std 883, Method 1012.1

°C/W

ΨJT

Junction-to-top-of-package characterization parameter, 0 m/sec airflow per JEDEC JESD51-2 (still air)

0.6

°C/W

1 The exposed pad on the bottom of the package must be soldered to ground to achieve the specified thermal performance.

2Results 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 AD9551 is specified for a case temperature (TCASE). To

ensure that TCASE is not exceeded, an airflow source can be used.

Use the following equation to determine the junction tempera-

ture on the application PCB:

= TCASE + (ΨJT × PD)

where:

is the junction temperature (°C).

TCASE

is the case temperature (°C) measured by the customer at

the top center of the package.

ΨJT

is the value indicated in Table 18.

is the power dissipation (see the Power Consumption section).

Values of θJA are provided for package comparison and PCB design

considerations. θJA can be used for a first-order approximation

of TJ using the following equation:

= TA + (θJA × PD)

where TA is the ambient temperature (°C).

Values of θJC are provided for package comparison and PCB

design considerations when an external heat sink is required.

Values of θJB are provided for package comparison and PCB

design considerations.

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