MC9RS08KA2 Datasheet, PDF (108/132 Pages) Freescale Semiconductor, Inc – Microcontrollers

Appendix A Electrical Characteristics
A.3 Thermal Characteristics
This section provides information about operating temperature range, power dissipation, and package
thermal resistance. Power dissipation on I/O pins is usually small compared to the power dissipation in
on-chip logic and voltage regulator circuits and it is user-determined rather than being controlled by the
MCU design. In order to take P_I/O into account in power calculations, determine the difference between
actual pin voltage and V_SS or V_DD and multiply by the pin current for each I/O pin. Except in cases of
unusually high pin current (heavy loads), the difference between pin voltage and V_SS or V_DD will be very
small.
Table A-2. Thermal Characteristics
Rating
Operating temperature range (packaged)
Maximum junction temperature
Thermal resistance ^1,2,3,4
Symbol
T_A
T_JMAX
Value
T_L to T_H
–40 to 85
105
Unit
°C
°C
6-pin DFN
8-pin PDIP
8-pin SOIC
1s
2s2p
θ_JA
1s
2s2p
1s
2s2p
225
53
°C/W
115
74
160
98
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 _{Junction to Ambient Natural Convection}
3 _{1s - Single Layer Board, one signal layer}
4 _{2s2p - Four Layer Board, 2 signal and 2 power layers}
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:
MC9RS08KA2 Series Data Sheet, Rev. 2
108
Freescale Semiconductor