LQFP64 datasheet(52/103 Pages) STMICROELECTRONICS

52 / 103 page

Electrical characteristics

SPC560P34L1, SPC560P34L3, SPC560P40L1, SPC560P40L3

52/103

Doc ID 16100 Rev 7

3.5

Thermal characteristics

3.5.1

Package thermal characteristics

3.5.2

General notes for specifications at maximum junction temperature

An estimation of the chip junction temperature, TJ, can be obtained from Equation 1:

Equation 1: TJ = TA + (RθJA * PD)

where:

TA = ambient temperature for the package (°C)

RθJA = junction-to-ambient thermal resistance (°C/W)

PD = power dissipation in the package (W)

The junction-to-ambient thermal resistance is an industry standard value that provides a

quick and easy estimation of thermal performance. Unfortunately, there are two values in

common usage: the value determined on a single layer board and the value obtained on a

board with two planes. For packages such as the PBGA, these values can be different by a

factor of two. Which value is closer to the application depends on the power dissipated by

other components on the board. The value obtained on a single layer board is appropriate

for the tightly packed printed circuit board. The value obtained on the board with the internal

planes is usually appropriate if the board has low power dissipation and the components are

well separated.

When a heat sink is used, the thermal resistance is expressed in Equation 2 as the sum of a

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

Table 12.

LQFP thermal characteristics

Symbol

Parameter

Conditions

Typical value

Unit

100-pin

64-pin

RθJA

Thermal resistance junction-to-ambient, natural

convection(1)

Single layer board—1s

°C/W

Four layer board—2s2p

°C/W

RθJB

Thermal resistance junction-to-board(2)

Four layer board—2s2p

°C/W

RθJCtop Thermal resistance junction-to-case (top)

(3)

Single layer board—1s

°C/W

ΨJB

Junction-to-board, natural convection(4)

Operating conditions

°C/W

ΨJC

Junction-to-case, natural convection(5)

Operating conditions

°C/W

Junction-to-ambient thermal resistance determined per JEDEC JESD51-7. Thermal test board meets JEDEC specification

for this package.

Junction-to-board thermal resistance determined per JEDEC JESD51-8. Thermal test board meets JEDEC specification for

the specified package. When Greek letters are not available, the symbols are typed as RthJB or Theta-JB.

Junction-to-case at the top of the package determined using MIL-STD 883 Method 1012.1. The cold plate temperature is

used for the case temperature. Reported value includes the thermal resistance of the interface layer.

Thermal characterization parameter indicating the temperature difference between the board and the junction temperature

per JEDEC JESD51-2. When Greek letters are not available, the thermal characterization parameter is written as Psi-JB.

Thermal characterization parameter indicating the temperature difference between the package top and the junction

temperature per JEDEC JESD51-2. When Greek letters are not available, the thermal characterization parameter is written

as Psi-JC.

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