EX128-CS100A datasheet(20/49 Pages) ACTEL

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eX Family FPGAs

1- 16

v4.3

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 Table 1-11 on page 1-13. For

example, the typical static power for eX128 at 3.3 V VCCI

is:

ICC * VCCA = 795 µA x 2.5 V = 1.99 mW

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 * VCCA

2 x F

where:

Equivalent capacitance is calculated by measuring ICCA 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 the

results can be used over a wide range of operating

conditions. Equivalent capacitance values are shown

below.

CEQ Values for eX Devices

The variable and fixed capacitance of other device

components must also be taken into account when

estimating the dynamic power dissipation.

Table 1-12

shows

the

capacitance

the

clock

components of eX devices.

The estimation of the dynamic power dissipation is a

piece-wise linear summation of the power dissipation of

each component.

Dynamic power dissipation

= VCCA

2 * [(m

c * Ceqcm * fmC)Comb Modules + (ms * Ceqsm *

fmS)Seq Modules + (n * Ceqi * fn)Input Buffers + (0.5 * (q1 *

Ceqcr * fq1) + (r1 * fq1))RCLKA + (0.5 * (q2 * Ceqcr * fq2) +

(r2 * fq2))RCLKB + (0.5 * (s1 * Ceqhv * fs1)+(Ceqhf *

fs1))HCLK] + VCCI

2 * [(p * (C

eqo + CL) * fp)Output Buffers]

where:

CEQ = Equivalent capacitance

= switching frequency

Combinatorial modules (Ceqcm) 1.70 pF

Sequential modules (Ceqsm)

1.70 pF

Input buffers (Ceqi)

1.30 pF

Output buffers (Ceqo)

7.40 pF

Routed array clocks (Ceqcr)

1.05 pF

Table 1-12 • Capacitance of Clock Components of eX

Devices

eX64

eX128

eX256

Dedicated

array

clock

–

variable (Ceqhv)

0.85 pF

Dedicated array clock – fixed

(Ceqhf)

18.00 pF

20.00 pF

25.00 pF

Routed array clock A (r1)

23.00 pF

28.00 pF

35.00 pF

Routed array clock B (r2)

23.00 pF

28.00 pF

35.00 pF

= Number of combinatorial cells switching at

frequency fm, typically 20% of C-cells

= Number of sequential cells switching at

frequency fm, typically 20% of R-cells

= Number

input

buffers

switching

frequency fn, typically number of inputs / 4

= Number of output buffers switching at

frequency fp, typically number of outputs / 4

= Number of R-cells driven by routed array

clock A

= Number of R-cells driven by routed array

clock B

= Fixed capacitance due to routed array clock A

= Fixed capacitance due to routed array clock B

= Number of R-cells driven by dedicated array

clock

Ceqcm =

Equivalent capacitance of combinatorial

modules

EX128-CS100A Datasheet(PDF) 20 Page - Actel Corporation

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