SPC560B64L5 datasheet(63/134 Pages) STMICROELECTRONICS

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SPC560B54/6x

Electrical characteristics

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4.5.3

Power considerations

The average chip-junction temperature, TJ, in degrees Celsius, may be calculated using

<Cross Refs>Equation 1:

Equation 1: TJ = TA + (PD x RθJA)

Where:

TA is the ambient temperature in °C.

RθJA is the package junction-to-ambient thermal resistance, in °C/W.

PD is the sum of PINT and PI/O (PD = PINT + PI/O).

PINT is the product of IDD and VDD, expressed in watts. This is the chip internal

power.

PI/O represents the power dissipation on input and output pins; user determined.

Most of the time for the applications, PI/O< PINT and may be neglected. On the other hand,

PI/O may be significant, if the device is configured to continuously drive external modules

and/or memories.

An approximate relationship between PD and TJ (if PI/O is neglected) is given by:

Equation 2: PD = K / (TJ + 273 °C)

Therefore, solving equations <Cross Refs>1 and <Cross Refs>2:

Equation 3: K = PD x (TA + 273 °C) + RθJA x PD

Where:

K is a constant for the particular part, which may be determined from <Cross

Refs>Equation 3 by measuring PD (at equilibrium) for a known TA. Using this value

RθJC CC

Thermal resistance, junction-

to-case(5)

Single-layer board — 1s

100

—

°C/W

144

—

176

—

Four-layer board — 2s2p

100

—

19.8

144

—

19.2

176

—

18.8

Thermal characteristics are targets based on simulation.

VDD = 3.3 V ± 10% / 5.0 V ± 10%, TA = −40 to 125 °C.

Junction-to-ambient thermal resistance determined per JEDEC JESD51-3 and JESD51-6. Thermal test board meets

JEDEC specification for this package. When Greek letters are not available, the symbols are typed as RthJA and RthJMA.

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.

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. When Greek letters

are not available, the symbols are typed as RthJC.

Table 15.

LQFP thermal characteristics(1) (continued)

Symbol

Parameter

Conditions(2)

Pin count

Value

Unit

Min

Typ

Max

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