Power Considerations
Last Edit July 22, 2001
Step 7: Compute the WorstCase Overhead Current
Multiply both the IEE and ICC overhead currents by the worstcase current
multiplier for the overhead current (WCCM3) to obtain the worstcase overhead
currents
IoverheadCCwc = WCCM3 * IoverheadCC
IoverheadEEwc = WCCM3 * IoverheadEE
Step 8: Sum the ICC and IEE Currents
Sum the internal macro, interface macro, and overhead worstcase currents,
keeping ICC and IEE separate to find the total IEE and ICC worstcase
currents
ICCwc = SUM IinternalCCwc + IinterfaceCCwc + IoverheadCCwc
IEEwc = SUM IinternalEEwc + IinterfaceEEwc + IoverheadEEwc
Step 9: Multiply by the WorstCase Voltage
The worstcase voltage is dependent on whether the circuit is commercial
or military and the specified allowed power supply variations. The array
data sheet carries this information. The typical variation is shown below.
For commercial circuits, with a 5.2V or a +5V supply, the voltage variation
is usually ±5%. For commercial circuits using VEE = 4.5V, the variation
is ±7%
For military circuits, the voltage variation is usually ±10%. Note: The
worstcase voltage for the 4.5V supply as listed on the Q20000 data sheet,
where 4.5V supply varies ±7%. The worstcase voltage is taken as 4.8V
for military or commercial circuits
Table 714 Example WorstCase Voltages
Nominal 
Commercial 
MILITARY 
+5.0V 
+5.25V 
+5.5V 
5.2V 
5.46V 
5.72V 
4.5V 
4.8V 
4.8V 
Multiply the worstcase DC current by the appropriate worstcase voltage:
PEEDC = IEEwc * VEEwc
PCCDC = ICCwc * VCCwc
This product is the worstcase DC power due to the macros on the array.
