PPC5605BECLLR datasheet(18/92 Pages) FREESCALE

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MPC5607B Microcontroller Data Sheet, Rev. 3

Preliminary—Subject to Change Without Notice

Electrical characteristics

Freescale Semiconductor

3.5.3

Power considerations

The average chip-junction temperature, TJ, in degrees Celsius, may be calculated using Equation 1:

TJ = TA + (PD x RθJA)

Eqn. 1

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:

PD = K / (TJ + 273 °C)

Eqn. 2

Therefore, solving equations 1 and 2:

K = PD x (TA + 273 °C) + RθJA x PD

Eqn. 3

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 1 and 2

iteratively for any value of TA.

3.6

I/O pad electrical characteristics

3.6.1

I/O pad types

The device provides four main I/O pad types depending on the associated alternate functions:

•

Slow pads - are the most common pads, providing a good compromise between transition time and low

electromagnetic emission.

•

Medium pads - provide transition fast enough for the serial communication channels with controlled current to reduce

electromagnetic emission.

Table 11. 208 MAPBGA thermal characteristics1

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

Symbol

Parameter

Conditions

Value

Unit

RθJA

—

Thermal

resistance,

junction-to-am

bient natural

convection2

2 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.

Single-layer

board—1s

TBD

°C/W

Four-layer

board—2s2p

PPC5605BECLLR Datasheet(PDF) 18 Page - Freescale Semiconductor, Inc

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