SPC56AP54X datasheet(56/104 Pages) STMICROELECTRONICS

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Electrical characteristics

SPC56xP54x, SPC56xP60x

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Doc ID 18340 Rev 3

3.5.1

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 + (RJA × PD)

where:

= ambient temperature for the package (oC)

RJA

= junction to ambient thermal resistance (oC/W)

= 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:

Equation 2

RJA = RJC + RCA

where:

RJA

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

RJC

= junction to case thermal resistance (°C/W)

RCA

= case to ambient thermal resistance (°C/W)

Table 13.

Thermal characteristics for 100-pin LQFP

Symbol

Parameter

Conditions

Typical value Unit

RJA

Thermal resistance junction-to-ambient,

natural convection(1)

Single layer board—1s

47.3

°C/W

Four layer board—2s2p

35.6

°C/W

RJB

Thermal resistance junction-to-board(2)

Four layer board—2s2p

19.1

°C/W

RJCtop

Thermal resistance junction-to-case (top)(3) Single layer board—1s

9.1

°C/W



Junction-to-board, natural convection(4)

Operating conditions

19.1

°C/W



Junction-to-case, natural convection(5)

Operating conditions

1.1

°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.

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 case 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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