ADSP-21MOD980N Datasheet, PDF (21/42 Pages) Analog Devices – MultiPort Internet Gateway Processor

PRELIMINARY TECHNICAL DATA
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ADSP-21mod980N
POWER DISSIPATION
To determine total power dissipation in a specific applica-
tion, the following equation should be applied for each
output:
C ؋ V_DD² ؋ f
C = load capacitance
f = output switching frequency
Example:
In an application where an external host is accessing inter-
nal memory and no other outputs are active, power
dissipation is calculated as follows:
Assumptions:
Assumptions:
• External data memory is accessed every fourth cycle
with 50% of the address pins switching.
• External data memory writes occur every fourth cycle
with 50% of the data pins switching.
• Each address and data pin has a 64 pF total load at the
pin.
• Application operates at V_DDEXT = 3.3 V and t_CK = 30 ns.
Total Power Dissipation = P_INT + (C ؋V_DDEXT² ؋ f)
P _INT= internal power dissipation from Figure 15
(C ؋ V_DDEXT² ؋ f) is calculated for each output, as in the
example in Table 7.
Table 7. Example Power Dissipation Calculation
Parameters
# of Pins
× C (pF)
Address
8
64
Data Output, WR
9
64
× V_DDEXT² (V)
3.3²
3.3²
× f (MHz)
18.8
18.8
PD (mW)
104.8
117.9
222.7
Total power dissipation for this example is:
PD = P_INT + 222.7 mW
REV. PrB 6/2001
21