Power Considerations
Last Edit July 22, 2001
Case Study: AC Power Computation
The Q20000 Series AC power methodology [as of 1994] is detailed below
to allow sample computations and to provide some reference for analysis
of other arrays.
Step 1: Build the Macro Occurrence Table
A macro occurrence worksheet for interface and internal logic macros
can be constructed before design capture to assist in the computation
of total circuit power dissipation. A macro occurrence worksheet for the
interface and internal logic should provide:
 A list of the different macros differentiated by option;
 The number of times each macro appears on the schematics;
 The number of outputs the macro has.
The macros are differentiated by option if there is a difference in the
conversion constant. The number of outputs is required if that is the
sizing measure used by the vendor. If the number of gates rather than
the number of macros is required, a conversion factor in gates per macro
is supplied.
The AMCC MacroMatrix ERC produces a BiCMOS/Bipolar Power Computation
Worksheet that lists macros and their occurrences and which can be used
for manual AC power analysis.
Because of the use of several different conversion constants for the
Q20000 macros, the macros on the worksheet must be grouped within certain
types. The types are ECL Darlington outputs, ECL inputs and internal macros.
Other ECL outputs are not involved in the computation. TTL I/O macros
are not involved in the computation.
Step 2: Find the number of Darlington Outputs
Using the macro occurrence worksheet, find the number of Darlington outputs.
For AMCC customers, the number of Darlington outputs can be determined
from the AMCC I/O statistics ERC report and from the AMCC AC
Bipolar/BiCMOS Macro Occurrence worksheet.
Count the number of Darlington output macros switching at the fastest
frequency. Count the number of Darlington output macros switching at the
next fastest frequency. Repeat until all Darlington output macros are
accounted for.
Step 3: Compute AC Power For all ECL Darlington Output Macros
Using the counts from step 2, compute the AC power dissipated by the
ECL Darlington outputs used in the circuit. For AMCC arrays, use:
PacDARoutputs = f * n * 15 microwatts
where
f = maximum frequency of the Darlington outputs in MHz
n = number of ECL Darlington output macros toggling at frequency f
conversion factor = 15 microwatt/macroMHz for Q20000 Series
 Compute the AC power due to those macros switching at the fastest
frequency.
 Compute the AC power due to those macros switching at the next fastest
frequency.
 Repeat until all Darlington output macros are accounted for and sum
the results.
Step 4: Find the Number of ECL Inputs
Using the macro occurrence worksheet, find the number of ECL input macros.
For AMCC customers, the number of ECL input macros can be determined from
the AMCC I/O statistics ERC report and from the AMCC AC Bipolar/BiCMOS
Macro Occurrence worksheet.
 Count the number of ECL input macros switching at the fastest frequency.
 Count the number of ECL input macros switching at the next fastest
frequency.
 Repeat until all ECL input macros are accounted for and sum the results.
