MPC5644B View Datasheet(PDF) - Freescale Semiconductor
Part Name
Description
MFG CO.
'MPC5644B' PDF : 114 Pages View PDF
4.5 Thermal characteristics
4.5.1 Package thermal characteristics
Table 11. LQFP thermal characteristics1
Symbol
RJA
CC
C
Parameter
Conditions2 Pin count
Min
D Thermal resistance, Single-layer
176
—
junction-to-ambient board—1s
natural convection4
208
—
Value3
Typ
—
—
Unit
Max
385 °C/W
416 °C/W
RJA
CC
D Thermal resistance, Four-layer
176
—
—
31 °C/W
junction-to-ambient board—2s2p7
natural convection7
208
—
—
34 °C/W
1 Thermal characteristics are targets based on simulation that are subject to change per device characterization.
2 VDD = 3.3 V ± 10% / 5.0 V ± 10%, TA = 40 to 125 °C.
3 All values need to be confirmed during device validation.
4 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.
5 Junction-to-Ambient thermal resistance determined per JEDEC JESD51-3 and JESD51-6.
6 Junction-to-Ambient thermal resistance determined per JEDEC JESD51-2 and JESD51-6
7 Junction-to-Board thermal resistance determined per JEDEC JESD51-8.
Table 12. 256 MAPBGA thermal characteristics1
Symbol C
Parameter
Conditions
Value
Unit
RJA CC — Thermal resistance, junction-to-ambient
natural convection
Single-layer board—1s
Four-layer board—2s2p
432
°C/W
263
1 Thermal characteristics are targets based on simulation that are subject to change per device characterization.
2 Junction-to-ambient thermal resistance determined per JEDEC JESD51-2 with the single layer board horizontal.
Board meets JESD51-9 specification.
3 Junction-to-ambient thermal resistance determined per JEDEC JESD51-6 with the board horizontal.
4.5.2 Power considerations
The average chip-junction temperature, TJ, in degrees Celsius, may be calculated using Equation 1:
TJ = TA + (PD RJA)
Where:
TA is the ambient temperature in °C.
RJA is the package junction-to-ambient thermal resistance, in °C/W.
PD is the sum of PINT and PI/O (PD = PINT + PI/O).
PINT is the product of IDD and VDD, expressed in watts. This is the chip internal power.
PI/O represents the power dissipation on input and output pins; user determined.
Eqn. 1
MPC5646C Microcontroller Data Sheet, Rev. 3
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
45
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