AD9557SLASHPCBZ datasheet(52/92 Pages) AD

52 / 92 page

AD9557

Data Sheet

Rev. A | Page 52 of 92

THERMAL PERFORMANCE

Table 31. 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)

30.2

°C/W

θJMA

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

26.4

°C/W

θJMA

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

23.6

°C/W

θJB

Junction-to-board thermal resistance, 0.0 m/sec airflow per JEDEC JESD51-8 (still air)

16.3

°C/W

θJC

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

2.2

°C/W

ΨJT

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

0.2

°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 if they are similar to those assumed in these calculations.

The AD9557 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 temperature on the

application PCB:

TJ = TCASE + (ΨJT × PD)

where:

TJ 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 as indicated in Table 31.

PD is the power dissipation (see the Table 3).

Values of θJA are provided for package comparison and PCB

design considerations. θJA can be used for a first order approxi-

mation of TJ by the following equation:

TJ = 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.

AD9557/PCBZ Datasheet(PDF) 52 Page - Analog Devices

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