Datasheet

Electrical Characteristics
MCF51AC256 ColdFire Microcontroller Data Sheet, Rev.7
Freescale Semiconductor 19
The average chip-junction temperature (T
J
) in C can be obtained from:
T
J
= T
A
+ (P
D
 
JA
) Eqn. 1
where:
T
A
= Ambient temperature, C

JA
= Package thermal resistance, junction-to-ambient, C/W
P
D
= P
int
P
I/O
P
int
= I
DD
 V
DD
, Watts — chip internal power
P
I/O
= Power dissipation on input and output pins — user determined
For most applications, P
I/O
 P
int
and can be neglected. An approximate relationship between P
D
and T
J
(if P
I/O
is neglected) is:
P
D
= K  (T
J
+ 273C) Eqn. 2
Solving Equation 1 and Equation 2 for K gives:
K = P
D
 (T
A
+ 273C) + 
JA
 (P
D
)
2
Eqn. 3
where K is a constant pertaining to the particular part. K can be determined from Equation 3 by measuring
P
D
(at equilibrium) for a known T
A
. Using this value of K, the values of P
D
and T
J
can be obtained by
solving Equation 1 and Equation 2 iteratively for any value of T
A
.
2.4 Electrostatic Discharge (ESD) Protection Characteristics
Although damage from static discharge is much less common on these devices than on early CMOS
circuits, normal handling precautions should be used to avoid exposure to static discharge. Qualification
tests are performed to ensure that these devices can withstand exposure to reasonable levels of static
without suffering any permanent damage.
All ESD testing is in conformity with CDF-AEC-Q00 Stress Test Qualification for Automotive Grade
Integrated Circuits. (http://www.aecouncil.com/) This device was qualified to AEC-Q100 Rev E.
A device is considered to have failed if, after exposure to ESD pulses, the device no longer meets the
device specification requirements. Complete dc parametric and functional testing is performed per the
1
Junction temperature is a function of die size, on-chip power dissipation, package thermal
resistance, mounting site (board) temperature, ambient temperature, air flow, power dissipation
of other components on the board, and board thermal resistance
2
Junction to Ambient Natural Convection
3
1s — Single layer board, one signal layer
4
2s2p — Four layer board, 2 signal and 2 power layers