SPC56EC64L8 datasheet(54/118 Pages) STMICROELECTRONICS

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Electrical Characteristics

SPC564Bxx - SPC56ECxx

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Doc ID 17478 Rev 4

4.5.2

Power considerations

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

Equation 1:

Equation 1 TJ = TA + (PD × 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 Equation 1 and Equation 2:

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

Where:

K is a constant for the particular part, which may be determined from Equation 3

by measuring PD (at equilibrium) for a known TA. Using this value of K, the values

of PD and TJ may be obtained by solving equations Equation 1 and Equation 2

iteratively for any value of TA.

Thermal characteristics are targets based on simulation that are subject to change per device characterization.

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

All values need to be confirmed during device validation.

1s board as per standard Jedec (JESD51-7) in natural convection

2s2p board as per standard JEDEC (JESD51-7) in natural convection.

Table 13.

LBGA256 thermal characteristics(1)

Symbol

Parameter

Conditions

Value

Unit

RθJA CC —

Thermal resistance, junction-to-ambient

natural convection

Single-layer board—1s

TBD

°C/W

Four-layer board—2s2p

TBD

Thermal characteristics are targets based on simulation that are subject to change per device characterization.

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