P9221-R3 Datasheet

© 2017 Integrated Device Technology, Inc.

37

October 20, 2017

13. Application Information

13.1 Power Dissipation and Thermal Requirements

The use of integrated circuits in low-profile and fine-pitch surface-mount packages requires special attention to power dissipation. Many system-

dependent issues such as thermal coupling, airflow, added heat sinks, convection surfaces, and the presence of other heat-generating

components must be taken into consideration.

The P9221-R3 package has a maximum power dissipation of approximately 1.72W, which is governed by the number of thermal vias between

the package and the printed circuit board. The die’s maximum power dissipation is specified by the junction temperature and the package

thermal resistance. The WLCSP package has a typical θJA of 47ºC/W with 8 thermal vias and 77ºC/W with no thermal vias. Maximizing the

thermal vias is highly recommended.

The ambient temperature surrounding the P9221-R3 will also have an effect on the thermal limits of the printed circuit board (PCB). The main

factors influencing thermal resistance (θJA) are the PCB characteristics and thermal vias. For example, in a typical still-air environment, a

significant amount of the heat generated is absorbed by the PCB. Changing the design or configuration of the PCB changes the overall thermal

resistivity and therefore the board’s heat-sinking efficiency.

Three basic approaches for enhancing thermal performance are listed below:



Improving the power dissipation capability of the PCB design



Improving the thermal coupling of the component to the PCB



Introducing airflow into the system

As a first step, the maximum power dissipation for a given situation should be calculated using Equation 6:

PD(MAX) =

(TJ(MAX) − TAMB)

θJA

Equation 6

Where PD(MAX) = Maximum power dissipation

θJA = Package thermal resistance (°C/W)

TJ(MAX) = Maximum device junction temperature (°C)

TAMB = Ambient temperature (°C)

The maximum recommended junction temperature (TJ(MAX)) for the P9221-R3 device is 125°C. The thermal resistance of the 52-WLCSP

package (AHG52) is nominally θJA=47°C/W with 8 thermal vias. Operation is specified to a maximum steady-state ambient temperature (TAMB)

of 85°C. Therefore, the maximum recommended power dissipation is given by Equation 7.

PD(MAX) =

(

125°C − 85°C)

47°C/W

≅ 0.85 Watt

Equation 7

All the above-mentioned thermal resistances were determined with the P9221-R3 mounted on a standard board of the dimensions and

characteristics specified by the JEDEC 51 standard.