7
COMMERCIALTEMPERATURERANGE
IDT72V3624/72V3634/72V3644 3.3V CMOS SyncBiFIFOTM WITH BUS-MATCHING
256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2
DETERMINING ACTIVE CURRENT CONSUMPTION AND POWER DISSIPATION
The ICC(f) current for the graph in Figure 1 was taken while simultaneously reading and writing a FIFO on the IDT72V3624/72V3634/72V3644 with
CLKA and CLKB set to fS. All data inputs and data outputs change state during each clock cycle to consume the highest supply current. Data outputs were
disconnected to normalize the graph to a zero capacitance load. Once the capacitance load per data-output channel and the number of these device's
inputs driven by TTL HIGH levels are known, the power dissipation can be calculated with the equation below.
CALCULATING POWER DISSIPATION
With ICC(f) taken from Figure 1, the maximum power dissipation (PT) of these FIFOs may be calculated by:
PT = VCC x ICC(f) +
Σ(CL x VCC2 x fo)
N
where:
N
=
number of used outputs (36-bit (long word), 18-bit (word) or 9-bit (byte) bus size)
CL
=
output capacitance load
fo
=
switching frequency of an output
Figure 1. Typical Characteristics: Supply Current (ICC) vs. Clock Frequency (fS)
010
20
30
40
50
60
70
0
25
50
75
100
125
150
VCC = 3.3V
fS
Clock Frequency
MHz
ICC(f)
Supply
Current
mA
fdata = 1/2 fS
TA = 25οC
CL = 0 pF
VCC = 3.0V
VCC = 3.6V
4664 drw03
175
200
80
90
100