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## TS68040DESC01YCA View Datasheet(PDF) - Atmel Corporation

 Part Name TS68040DESC01YCA Atmel Corporation Description Third-Generation 32-bit Microprocessor
TS68040DESC01YCA Datasheet PDF : 49 Pages
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 Relationships Between Thermal Resistances and Temperatures Thermal Management Techniques To calculate the specific power dissipation of a specific design, the termination method of each signal must be considered. For example, a signal output that is not connected would not dissipate any additional power if it were configured in the large buffer rather than the small buffer mode. Since the maximum operating junction temperature has been specified to be 125°C. The maximum case temperature, TC, in °C can be obtained from: TC = TJ - PD · ΦJC (2) where: TC = Maximum case temperature TJ = Maximum junction temperature PD = Maximum power dissipation of the device ΦJC = Thermal resistance between the junction of the die and the case In general, the ambient temperature, TA, in °C is a function of the following formula: TA = TJ - PD · ΦJC - PD · ΦCA (3) Where the thermal resistance from case to ambient, ΦCA, is the only user-dependent parameter once a buffer output configuration has been determined. As seen from equa- tion (3), reducing the case to ambient thermal resistance increases the maximum operating ambient temperature. Therefore, by utilizing such methods as heat sinks and ambient air cooling to minimize the ΦCA, a higher ambient operating temperature and/or a lower junction temperature can be achieved. However, an easier approach to thermal evaluation uses the following formulas: TA = TJ - PD · ΦJA (4) or alternatively, TJ = TA - PD · ΦJA (5) where: ΦJA = thermal resistance from the junction to the ambient (ΦJC + ΦCA). This total thermal resistance of a package, ΦJA, is a combination of its two components, ΦJC and ΦCA. These components represent the barrier to heat flow from the semicon- ductor junction to the package (case) surface (ΦJC) and from the case to the outside ambient (ΦJC). Although ΦJC is device related and cannot be influenced by the user, ΦCA is user dependent. Thus, good thermal management by the user can significantly reduce ΦCA achieving either a lower semiconductor junction temperature or a higher ambient operating temperature. To attain a reasonable maximum ambient operating temperature, a user must reduce the barrier to heat flow from the semiconductor junction to the outside ambient (ΦJA). The only way to accomplish this is to significantly reduce ΦCA by applying such thermal management techniques as heat sinks and ambient air cooling. The following paragraphs discuss some results of a thermal study of the TS68040 device without using any thermal management techniques; using only air-flow cooling, using only a heat sink, and using heat sink combined with air-flow cooling. 12 TS68040 2116A–HIREL–09/02