
Accelerator Series FPGAs – ACT 3 Family
R e visio n 3
2 - 13
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
Figure 2-10.To calculate the active power dissipated from the complete design, the switching frequency of each part
of the logic must be known.
EQ 5 shows a piece-wise linear summation over all components.
Power =VCC2 * [(m * CEQM * fm)modules + (n * CEQI * fn) inputs
+ (p * (CEQO+ CL) * fp)outputs
+ 0.5 * (q1 * CEQCR * fq1)routed_Clk1 + (r1 * fq1)routed_Clk1
+ 0.5 * (q2 * CEQCR * fq2)routed_Clk2
+ (r2 * fq2)routed_Clk2 + 0.5 * (s1 * CEQCD * fs1)dedicated_Clk
+ (s2 * CEQCI * fs2)IO_Clk]
EQ 5
Where:
m = Number of logic modules switching at fm
n = Number of input buffers switching at fn
p = Number of output buffers switching at fp
q1 = Number of clock loads on the first routed array clock
q2 = Number of clock loads on the second routed array clock
r1 = Fixed capacitance due to first routed array clock
r2 = Fixed capacitance due to second routed array clock
s1 = Fixed number of clock loads on the dedicated array clock
s2 = Fixed number of clock loads on the dedicated I/O clock
CEQM = Equivalent capacitance of logic modules in pF
CEQI = Equivalent capacitance of input buffers in pF
CEQO = Equivalent capacitance of output buffers in pF
CEQCR = Equivalent capacitance of routed array clock in pF
CEQCD = Equivalent capacitance of dedicated array clock in pF
CEQCI = Equivalent capacitance of dedicated I/O clock in pF
CL = Output lead capacitance in pF
fm = Average logic module switching rate in MHz
fn = Average input buffer switching rate in MHz
fp = Average output buffer switching rate in MHz
fq1 = Average first routed array clock rate in MHz
fq2 = Average second routed array clock rate in MHz
fs1 = Average dedicated array clock rate in MHz
fs2 = Average dedicated I/O clock rate in MHz
Table 2-10 CEQ Values for Microsemi FPGAs
Item
CEQ Value
Modules (CEQM)
6.7
Input Buffers (CEQI)7.2
Output Buffers (CEQO)
10.4
Routed Array Clock Buffer Loads (CEQCR)
1.6
0.7
I/O Clock Buffer Loads (CEQCI)
0.9