PC755 Datasheet, PDF (18/50 Pages) ATMEL Corporation – PowerPC 755/745 RISC Microprocessor

Thermal Management
Assistance
Figure 6. C4 Package with Head Sink Mounted to a Printed-circuit Board
External Resistance
Radiation Convection
Heat Sink
Internal Resistance
Printed ± Circuit Board
Thermal Interface Material
Die/Package
Die Junction
Package/Leads
External Resistance
Radiation Convection
Note the internal versus external package resistance.
The PC755 incorporates a thermal management assist unit (TAU) composed of a ther-
mal sensor, digital-to-analog converter, comparator, control logic, and dedicated
special-purpose registers (SPRs). Specifications for the thermal sensor portion of the
TAU are found in Table 9. More information on the use of this feature is given in the
Motorola PC755 RISC Microprocessor User’s manual.
Table 9. Thermal Sensor Specifications at Recommended Operating Conditions
(see Table 5)
Characteristic
Min
Max
Unit
Temperature range⁽¹⁾
0
127
°C
Comparator settling time⁽²⁾⁽³⁾
20
–
s
Resolution⁽³⁾
4
–
°C
Accuracy⁽³⁾
-12
+12
°C
Notes:
1. The temperature is the junction temperature of the die. The thermal assist unit’s raw
output does not indicate an absolute temperature, but must be interpreted by soft-
ware to derive the absolute junction temperature. For information about the use and
calibration of the TAU, see Motorola Application Note AN1800/D, “Programming the
Thermal Assist Unit in the PC750 Microprocessor”.
2. The comparator settling time value must be converted into the number of CPU clocks
that need to be written into the THRM3 SPR.
3. Guaranteed by design and characterization.
18 PC755/745
2138D–HIREL–06/03