www.irf.com

04/09/2009

7

iP2005CPbF

PD-60360

Applying the Safe Operating Area (SOA) Curve

The SOA graph incorporates power loss and thermal resistance information in a way that allows one

to solve for maximum current capability in a simplified graphical manner. It incorporates the ability to

solve thermal problems where heat is drawn out through the printed circuit board and the top of the

case. Please refer to International Rectifier Application Note AN1047 for further details on using this

SOA curve in your thermal environment.

Procedure

1. Calculate (based on estimated Power Loss) or measure the Case temperature on the device

and the board temperature near the device (1mm from the edge).

2. Draw a line from Case Temperature axis to the PCB Temperature axis.

4. Draw a horizontal line from the intersection of the vertical line with the SOA curve to the Y-axis

(Output Current).

The point at which the horizontal line meets the Y-axis is the SOA

continuous current.

Figure 11 SOA Example, Continuous current

≈ 31A for TPCB = 100ºC & TCASE = 110ºC