AFS090 datasheet(259/334 Pages) MICROSEMI

259 / 334 page

Fusion Family of Mixed Signal FPGAs

R e visio n 2

3 -9

The 1.76 W power is less than the required 3.00 W. The design therefore requires a heat sink, or the

airflow where the device is mounted should be increased. The design's total junction-to-air thermal

resistance requirement can be estimated by EQ 7:

EQ 7

Determining the heat sink's thermal performance proceeds as follows:

EQ 8

where

EQ 9

A heat sink with a thermal resistance of 5.01°C/W or better should be used. Thermal resistance of heat

sinks is a function of airflow. The heat sink performance can be significantly improved with increased

airflow.

Carefully estimating thermal resistance is important in the long-term reliability of an Microsemi FPGA.

Design engineers should always correlate the power consumption of the device with the maximum

allowable power dissipation of the package selected for that device.

Note: The junction-to-air and junction-to-board thermal resistances are based on JEDEC standard

(JESD-51) and assumptions made in building the model. It may not be realized in actual application and

therefore should be used with a degree of caution. Junction-to-case thermal resistance assumes that all

power is dissipated through the case.

Temperature and Voltage Derating Factors

θJA = 0.37°C/W

= Thermal resistance of the interface material between

the case and the heat sink, usually provided by the

thermal interface manufacturer

θSA = Thermal resistance of the heat sink in °C/W

Table 3-7 • Temperature and Voltage Derating Factors for Timing Delays

(normalized to TJ = 70°C, Worst-Case VCC = 1.425 V)

Array Voltage

VCC (V)

Junction Temperature (°C)

–40°C

0°C

25°C

70°C

85°C

100°C

1.425

0.88

0.93

0.95

1.00

1.02

1.05

1.500

0.83

0.88

0.90

0.95

0.96

0.99

1.575

0.80

0.85

0.87

0.91

0.93

0.96

ja(total)

TJ TA

–

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

100°C 70°C

–

3.00 W

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

10.00°C/W

JA(TOTAL)

–

13.33°C/W 8.28°C/W

–

0.37°C/W

–

5.01°C/W

AFS090 Datasheet(PDF) 259 Page - Microsemi Corporation

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