Specifications ispLSI 8840
Power Consumption
Power consumption in the ispLSI 8840 device depends
on two primary factors: the speed at which the device is
operating and the number of product terms used. The
product terms have a fuse-selectable speed/power
tradeoff setting. Each group of four product terms has a
single speed/power tradeoff control fuse that acts on the
complete group of four. The fast “high-speed” setting
operates product terms at their normal full power con-
sumption. For portions of the logic that can tolerate
longer propagation delays, selecting the slower “low-
power” setting will significantly reduce the power
dissipation for these product terms. Figure 10 shows the
relationship between power and operating speed.
Figure 10. Typical Device Power Consumption vs fmax
1200
1100
1000
900
800
700
600
500
400
300
200
ispLSI 8840
Turbo
Non-Turbo
0
10 20 30 40 50 60 70 80 90 100 110 120
fmax (MHz)
Notes: Configuration of 42 20-bit counters
Typical current at 5V, 25° C
I
I
can be estimated for the ispLSI 8840 using the following equation:
CC
= 48.0 + (# of Turbo PTs * 0.346) + (# of Non-Turbo PTs 0.165) + (# of Macrocells Used * fmax * AF * 0.049)
*
CC
# of Turbo PTs = Number of Turbo Product Terms Used in Design
# of Non-Turbo PTs = Number of Non-Turbo Product Terms Used in Design
fmax = Maximum Operating Frequency
Average Macrocell Toggle Frequency
AF (Activity Factor) =
Fmax
Note: An Activity Factor of 1.0 means all macrocell registers toggle at Fmax. An Activity Factor of 0.5 means the
average macrocell registers toggle at half of fmax.
The I
estimate is based on typical conditions (V
= 5.0V, room temperature) and an assumption of two GLB loads
CC
CC
on average exists. These values are for estimates only. Since the value of I
is sensitive to operating conditions
CC
and the program in the device, the actual I
should be verified.
CC
0127/8840
18
LATTICE [ LATTICE SEMICONDUCTOR ]
