MC9S12HZ256 Datasheet, PDF (628/692 Pages) Freescale Semiconductor, Inc – HCS12 Microcontrollers

Appendix A Electrical Characteristics
A.1.8 Power Dissipation and Thermal Characteristics
Power dissipation and thermal characteristics are closely related. The user must assure that the maximum
operating junction temperature is not exceeded. The average chip-junction temperature (T_J) in °C can be
obtained from:
TJ = TA + (PD • Θ_JA)
TJ = Junction Temperature, [°C ]
TA = Ambient Temperature, [°C ]
PD = Total Chip Power Dissipation, [W]
Θ_JA = Package Thermal Resistance, [°C/W]
The total power dissipation can be calculated from:
PD = PINT + PIO
PINT = Chip Internal Power Dissipation, [W]
PINT = IDDR ⋅ VDDR + IDDA ⋅ VDDA
∑ ^{PIO =}
i
RDSON
⋅
II
2
Oi
P_IO is the sum of all output currents on I/O ports associated with VDDX1,2 and VDDM1,2,3.
Table A-5. Thermal Package Characteristics¹
Num C
Rating
Symbol
Min
Typ
1 T Thermal Resistance LQFP112, single sided PCB²
θ_JA
–
–
2 T Thermal Resistance LQFP112, double sided PCB
θ_JA
–
–
with 2 internal planes³
3 T Junction to Board LQFP112
θ_JB
—
—
4 T Junction to Case LQFP112
θ_JC
—
—
5 T Junction to Package Top LQFP112
Ψ_JT
—
—
6 T Thermal Resistance QFP 80, single sided PCB
θ_JA
—
—
7 T Thermal Resistance QFP 80, double sided PCB
θ_JA
—
—
with 2 internal planes
8 T Junction to Board QFP80
θ_JB
—
—
9 T Junction to Case QFP80
θ_JC
—
—
10 T Junction to Package Top QFP80
Ψ_JT
—
—
1 _{The values for thermal resistance are achieved by package simulations}
Max
54
41
31
11
2
51
41
27
14
3
Unit
o_C/W
o_C/W
o_C/W
o_C/W
o_C/W
o_C/W
o_C/W
o_C/W
o_C/W
o_C/W
MC9S12HZ256 Data Sheet, Rev. 2.04
628
Freescale Semiconductor