eX Family FPGAs

v4.3

1-17

The eX, SX-A and RTSX-S Power Calculator can be used to

estimate the total power dissipation (static and dynamic)

of eX devices and can be found at

http://www.actel.com/products/rescenter/power/

Thermal Characteristics

The temperature variable in the Designer software refers

to

the

junction

temperature,

not

the

ambient

temperature. This is an important distinction because the

heat generated from dynamic power consumption is

usually hotter than the ambient temperature. EQ 1-1,

shown below, can be used to calculate junction

temperature.

EQ 1-1

Junction Temperature =

∆T + T

Where:

∆T = Temperature gradient between junction

(silicon) and ambient =

θ

P = Power

θ

located in the "Package Thermal Characteristics" section

below.

Package Thermal Characteristics

The device junction-to-case thermal characteristic is

θ

and the junction-to-ambient air characteristic is

θ

thermal characteristics for

θ

different air flow rates.

θ

The maximum junction temperature is 150

°C.

The maximum power dissipation allowed for eX devices

is a function of

θ

maximum power dissipation allowed for a TQFP 100-pin

package at commercial temperature and still air is as

follows:

Equivalent

capacitance

of

sequential

modules

= Equivalent capacitance of input buffers

= Equivalent capacitance of output buffers

=

Average

output

loading

capacitance,

typically 10 pF

= Average C-cell switching frequency, typically

F/10

= Average R-cell switching frequency, typically

F/10

fn

= Average input buffer switching frequency,

typically F/5

fp

= Average output buffer switching frequency,

typically F/5

fq1

= Frequency of routed clock A

fq2

= Frequency of routed clock B

fs1

= Frequency of dedicated array clock

Package Type

Pin Count

θ

jc

θ

ja

Units

Still Air

1.0 m/s

200 ft/min

2.5 m/s

500 ft/min

Thin Quad Flat Pack (TQFP)

64

12.0

42.4

36.3

34.0

°C/W

Thin Quad Flat Pack (TQFP)

100

14.0

33.5

27.4

25.0

°C/W

Chip Scale Package (CSP)

49

72.2

59.5

54.1

°C/W

Chip Scale Package (CSP)

128

54.1

44.6

40.6

°C/W

Chip Scale Package (CSP)

180

57.8

47.6

43.3

°C/W

Maximum Power Allowed

Max. junction temp. (

°C) Max. ambient temp. (°C)

–

θ

---------------------------------------------------------------------------------------------------------------------------------

150

°C70°C

–

33.5

°C/W

-----------------------------------

2.39W

=

=

=