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SN74ALVC7804_07 Datasheet, PDF (9/13 Pages) Texas Instruments – 512 × 18 FIRST-IN, FIRST-OUT MEMORY | |||
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SN74ALVC7804
512 Ã 18
FIRST-IN, FIRST-OUT MEMORY
SCAS432 â JANUARY 1995
TYPICAL CHARACTERISTICS
SUPPLY CURRENT
vs
CLOCK FREQUENCY
140
fdata = 1/2 fclock
120 TA = 75°C
CL = 0 pF
100
VCC = 3.6 V
VCC = 3.3 V
80
60
VCC = 3 V
40
20
0
0 10 20 30 40 50 60 70 80 90
fclock â Clock Frequency â MHz
Figure 4
calculating power dissipation
With ICC(f) taken from Figure 4, the dynamic power (Pd), based on all data outputs changing states on each read,
can be calculated by using:
Pd = VCC Ã [ICC(f) + (N Ã âICC Ã dc)] + â(CL Ã VCC2 Ã fo)
A more accurate total power (PT) can be calculated if quiescent power (Pq) is also taken into consideration.
Quiescent power (Pq) can be calculated using:
Pq = VCC Ã [ICCI + (N Ã âICC Ã dc)]
Total power will be:
PT = Pd + Pq
The above equations provide worst-case power calculations.
Where:
N = number of inputs driven by TTL levels
âICC = increase in power supply current for each input at a TTL high level
dc = duty cycle of inputs at a TTL high level of 3.4 V
CL = output capacitance load
fo = switching frequency of an output
ICCI = idle current, supply current when FIFO is idle â pF Ã fclock = 0.2 Ã fclock
(current is due to free-running clocks)
pF = power factor (the slope of idle ICC versus frequency)
ICC(f) = active current, supply current when FIFO is transferring data
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