WM8944BECSSLASHR datasheet(9/165 Pages) CIRRUS

9 / 165 page

WM8944B

Rev 4.3

THERMAL PERFORMANCE

Thermal analysis should be performed in the intended application to prevent the WM8944B from

exceeding maximum junction temperature. Several contributing factors affect thermal performance

most notably the physical properties of the mechanical enclosure, location of the device on the PCB in

relation to surrounding components and the number of PCB layers. Connecting the GND balls through

thermal vias and into a large ground plane will aid heat extraction.

Three main heat transfer paths exist to surrounding air as illustrated below in Figure 1:



Package top to air (radiation).



Package bottom to PCB (radiation).



Package balls to PCB (conduction).

W-CSP Package

PCB

Figure 1 Heat Transfer Paths

The temperature rise TR is given by TR = PD * ӨJA

PD is the power dissipated in the device.

JA is the thermal resistance from the junction of the die to the ambient temperature and is therefore a

measure of heat transfer from the die to surrounding air.

JA is determined with reference to JEDEC

standard JESD51-9.

The junction temperature TJ is given by TJ = TA +TR, where TA is the ambient temperature.

PARAMETER

SYMBOL

MIN

TYP

MAX

UNIT

Operating temperature range

-40

°C

Operating junction temperature

-40

125

°C

Thermal Resistance

(Junction to Board)

°C/W

Thermal Resistance

(Junction to Ambient)

°C/W

Note:

Junction temperature is a function of ambient temperature and of the device operating conditions. The ambient temperature

limits and junction temperature limits must both be observed.

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