7
COMMERCIALTEMPERATURERANGE
IDT723653/723663/723673 CMOS SyncFIFOTM WITH BUS-MATCHING
2,048 x 36 x 2, 4,096 x 36 x 2 and 8,192 x 36 x 2
Figure 1. Typical Characteristics: Supply Current (ICC) vs. Clock Frequency (fS)
0
10
20
3040
5060
70
0
50
100
150
200
250
300
VCC = 5.0V
fS
Clock Frequency MHz
ICC(f)
Supply
Current
mA
fdata = 1/2 fS
TA = 25oC
CL = 0 pF
VCC = 4.5V
VCC = 5.5V
5610 drw03
80
90
CALCULATING POWER DISSIPATION
The ICC(f) current for the graph in Figure 1 was taken while simultaneously reading and writing a FIFO on the IDT723653/723663/723673 with CLKA
andCLKBsettofS.Alldatainputsanddataoutputschangestateduringeachclockcycletoconsumethehighestsupplycurrent.Dataoutputsweredisconnected
to normalize the graph to a zero capacitance load. Once the capacitance load per data-output channel and the number of IDT723653/723663/723673 inputs
driven by TTL HIGH levels are known, the power dissipation can be calculated with the equation below.
With ICC(f) taken from Figure 1, the maximum power dissipation (PT) of these FIFOs may be calculated by:
PT = VCC x [ICC(f) + (N x
ICC x dc)] + Σ(CL x VCC2 X fo)
where:
N
=
number of inputs driven by TTL levels
ICC =
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
=
outputcapacitanceload
fo
=
switching frequency of an output