SPC574S60 datasheet(25/77 Pages) STMICROELECTRONICS

25 / 77 page

DS10601 Rev 6

25/77

SPC574Sx

Electrical characteristics

the air flow around the device, add a heat sink, change the mounting arrangement on the

printed circuit board, or change the thermal dissipation on the printed circuit board

surrounding the device. This description is most useful for packages with heat sinks where

90% of the heat flow is through the case to heat sink to ambient. For most packages, a

better model is required.

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 (YJT) 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:

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

ΨJPB = thermal characterization parameter (°C/W)

PD = power dissipation in the package (W)

3.8

Current consumption

The following table describes the consumption figures.

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