
Power Estimation and Management
Lattice Semiconductor
for LatticeECP/EC and LatticeXP Devices
12-2
Power Calculator Equations
The power equations used in the Power Calculator have the following general form:
Total DC Power (Resource)
= Total DC Power of Used Portion + Total DC Power of Unused Portion
= [DC Leakage per resource when Used * NRESOURCE]
+ [DC Leakage per resource when Unused * (NTOTAL RESOURCE - NRESOURCE)]
Where:
NTOTAL RESOURCE
is the total number of resources in a device.
NRESOURCE
is the number of resources used in the design.
The total DC power consumption for all the resources as per the design data is the sum of Quiescent Power and
the individual DC power of the resources in the Power Calculator.
Total DC Power (ICCAUX)
= KRESOURCE * 500 A + Typical Standby ICCAUX
Where:
KRESOURCE
is the number of reference input I/O such as HSTL/SSTL. For LVDS KRE-
SOURCE is number of inputs divided by two.
ICCAUX
is a DC current that does not change with I/O toggle rate or temperature.
Typical Standby ICCAUX is found in the data sheet.
The AC power, on the other hand, is governed by the equation:
Total AC Power (Resource)
=KRESOURCE * fMAX * AFRESOURCE * NRESOURCE
Where:
NTOTAL RESOURCE
is the total number of resources in a device.
NRESOURCE
is the number of resources used in the design.
KRESOURCE
is the power constant for the resource, measured in mW/MHz.
fMAX
is the maximum frequency at which the resource is running, measured in MHz.
AFRESOURCE
is the activity factor for the resource group, as a percentage (%) of switching
frequency.
Based on the above equations, if we wish to calculate the power consumption of the Slice portion, it will be as fol-
lows:
Total DC Power (Slice)
= Total DC Power of Used Portion + Total DC Power of Unused Portion
= [DC Leakage per Slice when Used * NSLICE]
+ [DC Leakage per Slice when Unused * (NTOTAL SLICE - NSLICE)]
Total AC Power (Slice)
=KSLICE * fMAX * AFSLICE * NSLICE
The DC and AC power, for a dedicated block, like DSP in LatticeECP devices, is governed by the following equa-
tions.
Total DC Power (Resource)
= DC Leakage per Resource * NRESOURCE