MC68306FC16 Datasheet, PDF (166/191 Pages) Motorola, Inc – Integrated EC000 Processor

8.3 POWER CONSIDERATIONS
The average chip-junction temperature, TJ, in °C can be obtained from:
TJ = TA + (PD • θ_JA)
(1)
where:
TA
θ_JA
PD
PINT
PI/O
= Ambient Temperature, °C
= Package Thermal Resistance, Junction-to-Ambient, °C/W
= PINT + PI/O
= IC
C ^{x VCC, Watts—Chip Internal Power}
= Power Dissipation on Input and Output Pins—User Determined
For most applications, PI/O < PINT and can be neglected.
An approximate relationship between PD and TJ (if PI/O is neglected) is:
PD = K ÷ (TJ + 273°C)
Solving Equations (1) and (2) for K gives:
K = PD • (TA + 273°C) + θ_JA • PD²
where K is a constant pertaining to the particular part. K can be determined from equation
(3) by measuring PD (at thermal equilibrium) for a known TA. Using this value of K, the
values of PD and TJ can be obtained by solving Equations (1) and (2) iteratively for any
value of TA.
8.4 AC ELECTRICAL SPECIFICATION DEFINITIONS
The AC specifications presented consist of output delays, input setup and hold times, and
signal skew times. All signals are specified relative to an appropriate edge of the clock and
possibly to one or more other signals.
The measurement of the AC specifications is defined by the waveforms shown in Figure
8-1. To test the parameters guaranteed by Motorola, inputs must be driven to the voltage
levels specified in that figure. Outputs are specified with minimum and/or maximum limits,
as appropriate, and are measured as shown in Figure 8-1. Inputs are specified with
minimum setup and hold times and are measured as shown. Finally, the measurement for
signal-to-signal specifications is also shown.
NOTE
The testing levels used to verify conformance to the AC
specifications do not affect the guaranteed DC operation of the
device as specified in the DC electrical specifications.
8-2
MC68306 USER'S MANUAL
MOTOROLA