Freescale Semiconductor *KE02 Series, Technical Data Manual

Page: 19 / 37

Table 10. Thermal attributes (continued)
Board type Symbol Description 64
LQFP
64 QFP 44
LQFP
32
LQFP
Unit Notes
Single-layer (1S) R
θ
JMA
Thermal resistance, junction
to ambient (200 ft./min. air
speed) 59 50 62 72 °C/W 1 , 3
Four-layer (2s2p) R
θ
JMA
Thermal resistance, junction
to ambient (200 ft./min. air
speed) 46 41 47 51 °C/W 1 , 3
— R
θ
JB
Thermal resistance, junction
to board 35 32 34 33 °C/W 4
— R
θ
JC
Thermal resistance, junction
to case 20 23 20 24 °C/W 5
—
Ψ
JT
Thermal characterization
parameter, junction to
package top outside center
(natural convection) 5 8 5 6 °C/W 6
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. Per JEDEC JESD51-2 with the single layer board (JESD51-3) horizontal.
3. Per JEDEC JESD51-6 with the board (JESD51-7) horizontal.
4. Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is measured
on the top surface of the board near the package.
5. Thermal resistance between the die and the solder pad on the bottom of the package. Interface resistance is ignored.
6. Thermal characterization parameter indicating the temperature difference between package top and the junction
temperature per JEDEC JESD51-2. When Greek letters are not available, the thermal characterization.
The average chip-junction temperature (T
J
) in °C can be obtained from:
T
J
= T
A
+ (P
D
×
θ
JA
)
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)
Solving the equations above for K gives:
K = P
D
× (T
A
+ 273 °C) +
θ
JA
× (P
D
)
2
Thermal specifications
KE02 Sub-Family Data Sheet, Rev4, 10/2014.
Freescale Semiconductor, Inc. 19