SPC563M60X datasheet(72/128 Pages) STMICROELECTRONICS

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Electrical characteristics

SPC563M64x, SPC563M60x

72/128

DocID14642 Rev 12

temperature at the perimeter (edge) of the package is approximately the same as the local

air temperature near the device. Specifying the local ambient conditions explicitly as the

board temperature provides a more precise description of the local ambient conditions that

determine the temperature of the device.

At a known board temperature, the junction temperature is estimated using the following

equation:

Equation 2 TJ = TB + (RJB * PD)

where:

TB = board temperature for the package perimeter (

oC)

RJB = junction-to-board thermal resistance (

oC/W) per JESD51-8S

PD = power dissipation in the package (W)

When the heat loss from the package case to the air does not factor into the calculation, an

acceptable value for the junction temperature is predictable. Ensure the application board is

similar to the thermal test condition, with the component soldered to a board with internal

planes.

The thermal resistance is expressed as the sum of a junction-to-case thermal resistance

plus a case-to-ambient thermal resistance:

Equation 3 RJA = RJC + RCA

where:

RJA = junction-to-ambient thermal resistance (

oC/W)

RJC = junction-to-case thermal resistance (

oC/W)

RCA = case to ambient thermal resistance (

oC/W)

RJC is device related and is not affected by other factors. The thermal environment can be

controlled to change the case-to-ambient thermal resistance, RCA. For example, change

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.

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

use the thermal characterization parameter (



JT) 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 + (JT x PD)

SPC563M60X Datasheet(PDF) 72 Page - STMicroelectronics

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