DSP56600FMSLASHAD datasheet(67/76 Pages) NXP

67 / 76 page

Preliminary

MOTOROLA

DSP56652 Technical Data Sheet

4-1

SECTION

DESIGN CONSIDERATIONS

HEAT DISSIPATION

An estimation of the chip junction temperature, TJ, in °C can be obtained from the

equation:

Equation 1:

Where:

TA = ambient temperature ûC

RqJA = package junction-to-ambient thermal resistance ûC/W

PD = power dissipation in package

Historically, thermal resistance has been expressed as the sum of a junction-to-case

thermal resistance and a case-to-ambient thermal resistance:

Equation 2:

Where:

RqJA = package junction-to-ambient thermal resistance ûC/W

RqJC = package junction-to-case thermal resistance ûC/W

RqCA = package case-to-ambient thermal resistance ûC/W

RqJC is device-related and cannot be influenced by the user. The user controls the

thermal environment to change the case-to-ambient thermal resistance, RqCA. For

example, the user can change the air flow around the device, add a heat sink, change

the mounting arrangement on the printed circuit board, or otherwise change the

thermal dissipation capability of the area surrounding the device on a printed circuit

board. This model is most useful for ceramic packages with heat sinks; ninety percent

of the heat flow is dissipated through the case to the heat sink and out to the ambient

environment. For ceramic packages, in situations where the heat flow is split between

a path to the case and an alternate path through the printed circuit board, analysis of

the device thermal performance may need the additional modeling capability of a

system level thermal simulation tool.

The thermal performance of plastic packages is more dependent on the temperature

of the printed circuit board to which the package is mounted. Again, if the

RqJA

()

RqJA

RqJC RqCA

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

DSP56600FM/AD Datasheet(PDF) 67 Page - NXP Semiconductors