6
Table 3-3 Thermal Characteristics
Value
Characteristic
Symbol
Unit
Notes
Comments
48-pin LQFP
Junction to ambient
RθJA
50.6
°C/W
2
Natural convection
Junction to ambient (@1m/sec)
RθJMA
47.4
39.1
°C/W
°C/W
2
Junction to ambient
Natural convection
Four layer board (2s2p)
Four layer board (2s2p)
RθJMA
(2s2p)
1,2
Junction to ambient (@1m/sec)
Junction to case
RθJMA
RθJC
ΨJT
37.9
17.3
°C/W
°C/W
°C/W
W
1,2
3
Junction to center of case
I/O pin power dissipation
Power dissipation
1.2
4, 5
P I/O
User Determined
P D = (IDD x VDD + P I/O
(TJ - TA) /RθJA
P D
)
W
Junction to center of case
PDMAX
W
7
Notes:
1. Theta-JA determined on 2s2p test boards is frequently lower than would be observed in an application.
Determined on 2s2p thermal test board.
2. Junction to ambient thermal resistance, Theta-JA (RθJA) was simulated to be equivalent to the JEDEC
specification JESD51-2 in a horizontal configuration in natural convection. Theta-JA was also simulated on
a thermal test board with two internal planes (2s2p where s is the number of signal layers and p is the number
of planes) per JESD51-6 and JESD51-7. The correct name for Theta-JA for forced convection or with the
non-single layer boards is Theta-JMA.
3. Junction to case thermal resistance, Theta-JC (RθJC ), was simulated to be equivalent to the measured values
using the cold plate technique with the cold plate temperature used as the "case" temperature. The basic cold
plate measurement technique is described by MIL-STD 883D, Method 1012.1. This is the correct thermal
metric to use to calculate thermal performance when the package is being used with a heat sink.
4. Thermal Characterization Parameter, Psi-JT (ΨJT ), is the "resistance" from junction to reference point
thermocouple on top center of case as defined in JESD51-2. ΨJT is a useful value to use to estimate junction
temperature in steady state customer environments.
5. Junction temperature is a function of 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.
6. See Section 5.1 from more details on thermal design considerations.
7. TJ = Junction Temperature
TA = Ambient Temperature
56F801 Technical Data, Rev. 17
16
Freescale Semiconductor
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