Motorola MC68340 사용자 설명서
11-2
MC68340 USER’S MANUAL
MOTOROLA
11.3 POWER CONSIDERATIONS
The average chip-junction temperature, TJ, in
°
C can be obtained from:
TJ = TA + (PD •
θ
JA)
(1)
where:
TA
= Ambient Temperature,
°
C
θ
JA
= Package Thermal Resistance, Junction-to-Ambient,
°
C/W
PD
= PINT + PI/O
PINT = ICC x
VCC, Watts—Chip Internal Power
PI/O
= 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 • PD
2
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.
(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.
11.4 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.
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
11-1. To test the parameters guaranteed by Motorola, inputs must be driven to the voltage
levels specified in the figure. Outputs are specified with minimum and/or maximum limits,
as appropriate, and are measured as shown. Inputs are specified with minimum setup and
hold times and are measured as shown. Finally, the measurement for signal-to-signal
specifications are shown.
11-1. To test the parameters guaranteed by Motorola, inputs must be driven to the voltage
levels specified in the figure. Outputs are specified with minimum and/or maximum limits,
as appropriate, and are measured as shown. Inputs are specified with minimum setup and
hold times and are measured as shown. Finally, the measurement for signal-to-signal
specifications are shown.
Note that 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
characteristics.
affect the guaranteed DC operation of the device as specified in the DC electrical
characteristics.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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