Power Considerations
Last Edit July 22, 2001
Case Study: DC Power Computation
The Q20000 Series DC power methodology is detailed below to allow sample
computations and to provide some reference for analysis of other arrays.
The method can be modified to apply to all AMCC arrays, independent of
their technology, and to apply to other vendor arrays
Steps Required To Compute DC Power:  Example Array Series
Step 1: Build the Macro Occurrence Table
A macro occurrence table can be constructed before design capture to
assist in the manual computation of interface current and power dissipation.
A macro occurrence table should provide the data necessary to compute
the worstcase DC power dissipated by the circuit. (This table approach
can be used with macros that specify current or macros that specify power.)
Macro
Name 
Number of Macro
Occurrences 
Macro
ICC 
Macro
IEE 
Total
ICC 
Total
IEE 
AMCC MacroMatrix ERC power computations are done with the worststate
current value, assuming the worst "state" always for those macros specified
with HIGH and LOW or ENABLED and DISABLED current. The power dissipation
value computed will be conservative. A manual computation can be made
to adjust the current used for these statedependent macros
Identify those macros where some assumption must be made on the value
of the current to be used in the table. They will need to be identified
during design submission
Step 2: Find the Total Interface Macro Current
The macro current for individual interface macros is multiplied by the
number of occurrences to determine the total typical current resulting
from the use of that macro in the circuit. Change the labels if power
has been specified
Compute the total current used by all occurrences of each interface macro
and sum these totals to find the total IEE and ICC interface current
IinterfaceCC = SUM INTERFACE MACROS ICC CURRENT
IinterfaceEE = SUM INTERFACE MACROS IEE CURRENT
Unless the circuit uses a singlepower supply these two sums must be kept
separate
Step 3: Compute the WorstCase Interface Current
Multiply both sums by the worstcase current multiplier (WCCM1) for the
interface macros to obtain the worstcase current due to interface macros
IinterfaceCCwc = WCCM1 * IinterfaceCC
IinterfaceEEwc = WCCM1 * IinterfaceEE
The Q20000 Series uses three worstcase current multipliers, one for
core macros, one for interface macros and one for overhead current. Other
arrays may be specified with one multiplier or may vary the multiplier
or adjustment factor based on the product grade
Table 712 Example WorstCase Current Multipliers
Interface 
Internal 
Overhead 
WCCM1 
WCCM2 
WCCM3 
1.30 
1.25 
1.25 
