MC68HC16Z1CAG16 Datasheet, PDF (289/500 Pages) Freescale Semiconductor, Inc – M68HC16Z Series users manual

Freescale Semiconductor, Inc.
Table A-6 Thermal Characteristics
Num
Characteristic
Symbol
Value
Unit
Thermal Resistance
1 Plastic 132-Pin Surface Mount
Plastic 144-Pin Surface Mount
Θ_JA
38
°C/W
49
The average chip-junction temperature (T_J) in C can be obtained from:
T_J = T_A + (P_D × Θ_JA) (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:
P_D = K ÷ (T_J + 273°C) (2)
Solving equations 1 and 2 for K gives:
K = P_D × (T_A + 273°C) + Θ_JA × P_D2 ⁽³⁾
where K is a constant pertaining to the particular part. K can be determined from equation (3)
by measuring P_D (at equilibrium) for a known T_A. Using this value of K, the values of P_D and
T_J can be obtained by solving equations (1) and (2) iteratively for any value of T_A.
M68HC16 Z SERIES
ELECTRICAL CHARACTERISTICS
USER’S MANUAL
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