PD-60325

iP2005APbF

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.

3.Draw a vertical line from the T

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 10 SOA Example, Continuous current

≈ 31A for T

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2/8/2008

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