79R4640-180DU Ver la hoja de datos (PDF) - Integrated Device Technology
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79R4640-180DU Datasheet PDF : 23 Pages
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IDT79RC4640™
If the conditions are not correct when the WAIT instruction finishes the
W pipe-stage (i.e. the SysAd bus is not idle), the WAIT is treated as a
NOP.
Once the CPU is in Standby Mode, any interrupt, including the inter-
nally generated timer interrupt, will cause the CPU to exit Standby
Mode.
Thermal Considerations
The RC4640 utilizes special packaging techniques to improve the
thermal properties of high-speed processors. The RV4640 is packaged
using cavity-up packaging in a 128-pin thermally enhanced PQFP
package (“DU”) with a drop-in heat spreader, for devices with low peak
power. The R4640 utilizes the PQFP package for higher power
consumption devices (the “DZ” package), which is an all-aluminum
package with the die attached to a normal copper lead frame mounted to
the aluminum casing.
Due to the heat-spreading effect of the aluminum, the PQFP
package allows for an efficient thermal transfer between the die and the
case. The aluminum offers less internal resistance from one end of the
package to the other, reducing the temperature gradient across the
package and therefore presenting a greater area for convection and
conduction to the PCB for a given temperature. Even nominal amounts
of air flow will dramatically reduce the junction temperature of the die,
resulting in cooler operation. The PQFP package is pin and socket
compatible with the 128-pin QFP package.
The R4640 and the RV4640 are guaranteed in a case temperature
range of 0°C to +85°C for commercial temperature parts and the
RV4640 in a case temperature range of -40°C to +85°C for industrial
temperature parts. The type of package, speed (power) of the device,
and air flow conditions affect the equivalent ambient temperature condi-
tions that will meet this specification.
The equivalent allowable ambient temperature, TA, can be calculated
using the thermal resistance from case to ambient (∅CA) of the given
package. The following equation relates ambient and case tempera-
tures:
TA = TC - P * ∅CA
where P is the maximum power consumption at hot temperature,
calculated by using the maximum ICC specification for the device.
Typical values for ∅CA at various air flows are shown in Table 5.
∅CA
Airflow (ft/min) 0 200 400 600 800 1000
128 PQFP (DU)
17 9
7
5
4
3
128 PQFP (DZ)
20 12 9.5 8
7
6.5
Table 5 Thermal Resistance (∅CA) at Various Airflows
Note that the RC4640 implements advanced power management to
substantially reduce the average power dissipation of the device. This
operation is described in the IDT79RC4640/ IDT79RC4650 RISC
Processor Hardware User’s Manual.
MasterClock
SysAD
SysCmd
ValidOut
ValidIn
RdRdy
WrRdy
Release
Addr
Read
Data0 Data1
CData CData
Data6 Data7
CData CEOD
Figure 3 RC4640 Block Read Request
8 of 23
December 5, 2008
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