SPC582BX datasheet(103/115 Pages) STMICROELECTRONICS

103 / 115 page

DS11597 Rev 4

103/115

SPC582Bx

Package information

103

A more accurate two-resistor thermal model can be constructed from the junction-to-board

thermal resistance and the junction-to-case thermal resistance. The junction-to-case

thermal resistance describes when using a heat sink or where a substantial amount of heat

is dissipated from the top of the package. The junction-to-board thermal resistance

describes the thermal performance when most of the heat is conducted to the printed circuit

board. This model can be used to generate simple estimations and for computational fluid

dynamics (CFD) thermal models. More accurate compact Flotherm models can be

generated upon request.

To determine the junction temperature of the device in the application on a prototype board,

use the thermal characterization parameter (

ΨJT) to determine the junction temperature by

measuring the temperature at the top center of the package case using the following

equation:

Equation 4

TJ = TT + (ΨJT x PD)

where:

TT = thermocouple temperature on top of the package (°C)

ΨJT = thermal characterization parameter (°C/W)

PD = power dissipation in the package (W)

The thermal characterization parameter is measured in compliance with the JESD51-2

specification using a 40-gauge type T thermocouple epoxied to the top center of the

package case. Position the thermocouple so that the thermocouple junction rests on the

package. Place a small amount of epoxy on the thermocouple junction and approximately 1

mm of wire extending from the junction. Place the thermocouple wire flat against the

package case to avoid measurement errors caused by the cooling effects of the

thermocouple wire.

When board temperature is perfectly defined below the device, it is possible to use the

thermal characterization parameter (

ΨJPB) to determine the junction temperature by

measuring the temperature at the bottom center of the package case (exposed pad) using

the following equation:

Equation 5

TJ = TB + (ΨJPB x PD)

where:

TT = thermocouple temperature on bottom of the package (°C)

ΨJT = thermal characterization parameter (°C/W)

PD = power dissipation in the package (W)

SPC582BX Datasheet(PDF) 103 Page - STMicroelectronics

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