Datasheet

Electrical Characteristics
MC9S08GT16A/GT8A Data Sheet, Rev. 1
Freescale Semiconductor 261
The average chip-junction temperature (T
J
) in °C can be obtained from:
T
J
= T
A
+ (P
D
×θ
JA
) Eqn. A-1
where:
T
A
= Ambient temperature, °C
θ
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. A-2
Solving equations 1 and 2 for K gives:
K = P
D
× (T
A
+ 273°C) + θ
JA
× (P
D
)
2
Eqn. A-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 equations 1 and 2 iteratively for any value of T
A
.
Table A-3. Thermal Characteristics
Rating Symbol Value Unit
Operating temperature range
(packaged)
T
A
T
L
to T
H
–40 to 125
°C
Thermal resistance
1s board type
48-pin QFN 84
44-pin QFP θ
JA
1, 2
1
Junction temperature is a function of die size, on-chip power dissipation, package
thermal resistance, mounting site (board) temperature, ambient temperature, airflow,
power dissipation of other components on the board, and board thermal resistance.
2
Per SEMI G38-87 and JEDEC JESD51-2 with the single layer board horizontal.
Single layer board is designed per JEDEC JESD51-3.
72 °C/W
42-pin SDIP 62
32-pin QFN 99
Thermal resistance
2s2p board type
48-pin QFN 26
44-pin QFP θ
JA
1,2
54 °C/W
42-pin SDIP 51
32-pin QFN 33