EX256-CS100A ACTEL [Actel Corporation], EX256-CS100A Datasheet - Page 20

• Manufacturer Part Number: EX256-CS100A
• Description: eX Family FPGAs
• Manufacturer: ACTEL [Actel Corporation]

Power Dissipation
Power consumption for eX devices can be divided into
two components: static and dynamic.
Static Power Component
The power due to standby current is typically a small
component of the overall power. Typical standby current
for eX devices is listed in the
example, the typical static power for eX128 at 3.3 V V
is:
I
Dynamic Power Component
Power dissipation in CMOS devices is usually dominated
by the dynamic power dissipation. This component is
frequency-dependent and a function of the logic and the
external I/O. Dynamic power dissipation results from
charging internal chip capacitance due to PC board
traces and load device inputs. An additional component
of the dynamic power dissipation is the totem pole
current in the CMOS transistor pairs. The net effect can
be associated with an equivalent capacitance that can be
combined with frequency and voltage to represent
dynamic power dissipation.
Dynamic power dissipation = CEQ * V
where:
CEQ = Equivalent capacitance
F
Equivalent capacitance is calculated by measuring I
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 V
Equivalent capacitance is frequency-independent, so the
results can be used over a wide range of operating
conditions. Equivalent capacitance values are shown
below.
1 -1 6
CC
eX Family FPGAs
* V
= switching frequency
CCA
= 795 µA x 2.5 V = 1.99 mW
Table 1-11 on page
CCA
2
x F
1-13. For
CCA
CC
CCI
at
.
v4.3
CEQ Values for eX Devices
Combinatorial modules (Ceqcm) 1.70 pF
Sequential modules (Ceqsm)
Input buffers (Ceqi)
Output buffers (Ceqo)
Routed array clocks (Ceqcr)
The variable and fixed capacitance of other device
components must also be taken into account when
estimating the dynamic power dissipation.
Table 1-12
components of eX devices.
Table 1-12 • Capacitance of Clock Components of eX
The estimation of the dynamic power dissipation is a
piece-wise linear summation of the power dissipation of
each component.
Dynamic power dissipation
= V
fm
C
(r2 * fq2))
fs1))
where:
m
m
n
p
q1
q2
r1
r2
s1
C
Dedicated
variable (Ceqhv)
Dedicated array clock – fixed
(Ceqhf)
Routed array clock A (r1)
Routed array clock B (r2)
eqcr
eqcm
c
s
S
CCA
)
Seq Modules
HCLK
* fq1) + (r1 * fq1))
= Number of combinatorial cells switching at
= Number of sequential cells switching at
= Number
= Number of output buffers switching at
2
= Number of R-cells driven by routed array
= Number of R-cells driven by routed array
= Fixed capacitance due to routed array clock A
= Fixed capacitance due to routed array clock B
= Number of R-cells driven by dedicated array
=
* [(m
] + V
frequency fm, typically 20% of C-cells
frequency fm, typically 20% of R-cells
frequency fn, typically number of inputs / 4
frequency fp, typically number of outputs / 4
clock A
clock B
clock
modules
Equivalent capacitance of combinatorial
RCLKB
array
Devices
shows
CCI
c
* C
+ (n * C
2
* [(p * (C
eqcm
+ (0.5 * (s1 * C
clock
of
the
* fm
eqi
RCLKA
input
–
eqo
* fn)
capacitance
C
)
18.00 pF 20.00 pF 25.00 pF
23.00 pF 28.00 pF 35.00 pF
23.00 pF 28.00 pF 35.00 pF
Comb Modules
0.85 pF
+ (0.5 * (q2 * C
+ C
eX64
buffers
Input Buffers
L
1.70 pF
1.30 pF
7.40 pF
1.05 pF
) * fp)
eqhv
0.85 pF
eX128
Output Buffers
switching
* fs1)+(C
of
+ (m
+ (0.5 * (q1 *
eqcr
the
s
* C
eX256
0.85 pF
* fq2) +
eqhf
eqsm
clock
]
at
*
*