Detailed Specifications
2- 4
R e v ision 8
Static Power Component
Microsemi FPGAs have small static power components that result in lower power dissipation than PALs
or PLDs. By integrating multiple PALs/PLDs into one FPGA, an even greater reduction in board-level
power dissipation can be achieved.
The power due to standby current is typically a small component of the overall power. Standby power is
calculated in
Table 2-5 for commercial, worst case conditions.
The static power dissipated by TTL loads depends on the number of outputs driving high or low and the
DC load current. Again, this value is typically small. For instance, a 32-bit bus sinking 4 mA at 0.33 V will
generate 42 mW with all outputs driving low, and 140 mW with all outputs driving high. The actual
dissipation will average somewhere between as I/Os switch states with time.
Active Power Component
Power dissipation in CMOS devices is usually dominated by the active (dynamic) power dissipation. This
component is frequency dependent, a function of the logic and the external I/O. Active power dissipation
results from charging internal chip capacitances of the interconnect, unprogrammed antifuses, module
inputs, and module outputs, plus external capacitance due to PC board traces and load device inputs.
An additional component of the active power dissipation is the totem-pole current in CMOS transistor
pairs. The net effect can be associated with an equivalent capacitance that can be combined with
frequency and voltage to represent active power dissipation.
Equivalent Capacitance
The power dissipated by a CMOS circuit can be expressed by
EQ 3.Power (W) = CEQ * VCC2 * F
EQ 3
Where:
CEQ is the equivalent capacitance expressed in pF.
VCC is the power supply in volts.
F is the switching frequency in MHz.
Equivalent capacitance is calculated by measuring ICC active at a specified frequency and voltage for
each circuit component of interest. Measurements have been made over a range of frequencies at a
fixed value of VCC. Equivalent capacitance is frequency independent so that the results may be used
over a wide range of operating conditions. Equivalent capacitance values are shown in
Table 2-6.
Table 2-5 Standby Power Calculation
ICC
VCC
Power
2 mA
5.25 V
10.5 mW
Table 2-6 CEQ Values for Microsemi FPGAs
Item
CEQ Value
Modules (CEQM)
5.8
Input Buffers (CEQI)
12.9
Output Buffers (CEQO)
23.8
Routed Array Clock Buffer Loads (CEQCR)3.9