VMV3 datasheet(21/212 Pages) MICROSEMI

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Military ProASIC3/EL Low Power Flash FPGAs

Revision 3

2-7

Thermal Characteristics

Introduction

The temperature variable in the Designer software refers to the junction temperature, not the ambient

temperature. This is an important distinction because dynamic and static power consumption cause the

chip junction temperature to be higher than the ambient temperature.

EQ 1 can be used to calculate junction temperature.

TJ = Junction Temperature = T + TA

EQ 1

where:

TA = Ambient Temperature

T = Temperature gradient between junction (silicon) and ambient T = ja * P

ja = Junction-to-ambient of the package. ja numbers are located in Table 2-4.

P = Power dissipation

Package Thermal Characteristics

The device junction-to-case thermal resistivity is

jc and the junction-to-ambient air thermal resistivity is

ja. The thermal characteristics for ja are shown for two air flow rates. The recommended maximum

junction temperature is 125°C. EQ 2 shows a sample calculation of the recommended maximum power

dissipation allowed for a 484-pin FBGA package at military temperature and in still air.

EQ 2

Maximum Power Allowed

Max. junction temp. (

C) Max. ambient temp. (C)

–



ja(C/W)

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

125

C70C

–

20.6

C/W

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

2.670

Table 2-4 •

Package Thermal Resistivities

Package Type

Device

Pin Count

jc

ja

Units

Still Air 200 ft./min.

500 ft./min.

Very Thin Quad Flat Pack (VQ100)

A3P250

100

10.0

35.3

29.4

27.1

C/W

Plastic Quad Flat Pack (PQ208)*

A3P1000

208

3.8

16.2

13.3

11.9

C/W

Fine Pitch Ball Grid Array (FBGA)

A3P1000

144

6.3

31.6

26.2

24.2

C/W

A3PE600L

484

9.5

27.5

21.9

20.2

C/W

A3PE3000L

484

4.7

20.6

15.7

14.0

C/W

A3PE3000L

896

2.4

13.6

10.4

9.4

C/W

* Embedded heatspreader

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