SN74ALVC7803 Datasheet, PDF (12/14 Pages) Texas Instruments – 512 × 18 CLOCKED FIRST-IN, FIRST-OUT MEMORY

SN74ALVC7803
512 × 18
CLOCKED FIRST-IN, FIRST-OUT MEMORY
SDAS274 – 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 – Clock Frequency – MHz
Figure 7
calculating power dissipation
With I_CCf taken from Figure 7, the dynamic power (P_d), based on all data outputs changing states on each read,
can be calculated by using:
P_d = V_CC × [I_CC(f) + (N × ∆I_CC × dc)] + ∑(C_L × V_CC2 × f_o)
A more accurate total power (P_T) can be calculated if quiescent power (Pq) is also taken into consideration.
Quiescent power (P_q) can be calculated using:
P_q = V_CC × [I_CCI + (N × ∆I_CC × dc)]
Total power would be:
P_T = P_d + P_q
The above equations provide worst-case power calculations.
Where:
N = number of inputs driven by TTL levels
∆I_CC = 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
C_L = output capacitance load
f_o = switching frequency of an output
I_CCI = idle current, supply current when FIFO is idle ≈ pF × f_clock = 0.2 × f_clock
(current is due to free-running clocks)
pF = power factor (the slope of idle current versus clock frequency).
I_CCf = active current, supply current when FIFO is transferring data
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