JA80386EXTC25 Datasheet, PDF (24/56 Pages) Intel Corporation – Intel386™ EX Embedded Microprocessor

Intel386™ EX Embedded Microprocessor
5.2
Component and Revision Identifiers
To assist users, the microprocessor holds a component identifier and revision identifier in its DX
register after reset. The upper 8 bits of DX hold the component identifier, 23H. (The lower nibble,
3H, identifies the Intel386 architecture, while the upper nibble, 2H, identifies the second member
of the Intel386 microprocessor family.)
The lower 8 bits of DX hold the revision level identifier. The revision identifier will, in general,
chronologically track those component steppings that are intended to have certain improvements or
distinction from previous steppings. The revision identifier will track that of the Intel386 CPU
whenever possible. However, the revision identifier value is not guaranteed to change with every
stepping revision or to follow a completely uniform numerical sequence, depending on the type or
intent of the revision or the manufacturing materials required to be changed. Intel has sole
discretion over these characteristics of the component. The initial revision identifier for the
Intel386 EX microprocessor is 09H.
5.3
Package Thermal Specifications
The Intel386 EX microprocessor is specified for operation with a minimum case temperature
(T_CASE(MIN)) of -40° C and a maximum case temperature (T_CASE(MAX)) dependent on power
dissipation (see Figures 4 through 7). The case temperature can be measured in any environment to
determine whether the microprocessor is within the specified operating range. The case
temperature should be measured at the center of the top surface opposite the pins.
An increase in the ambient temperature (T_A) causes a proportional increase in the case temperature
(T_CASE) and the junction temperature (T_J), which is the junction temperature on the die itself. A
packaged device produces thermal resistance between junction and case temperatures (θ_JC) and
between junction and ambient temperatures (θ_JA). The relationships between the temperature and
thermal resistance parameters are expressed by these equations:
T_J = T_CASE + P × θ_JC
T_A = T_J – P × θ_JA
T_CASE = T_A + P × [θ_JA – θ_JC]
P = power dissipated as heat = V_CC × I_CC
A safe operating temperature can be calculated from the above equations by using the maximum
safe T_J of 120° C, the power drawn by the chip in the specific design, and the θ_JC value from Table
6. The θ_JA value depends on the airflow (measured at the top of the chip) provided by the system
ventilation, board layout, board thickness, and potentially other factors in the design of the
application. The θ_JA values are given for reference only and are not guaranteed.
Table 6. Thermal Resistances (0°C/W) θ_JA, θ_JC
Package
θ_JA vs. Airflow (ft/min)
θ_JC
0
100
200
132 PQFP
7
28
24
22
144 TQFP
4
36
31
27
Figures 4 through 7 provide maximum case temperature as a function of frequency.
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Datasheet