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iP2002PbF
Adjusting the Power Loss and SOA curves for different operating conditions
To make adjustments to the power loss curves in Fig. 1, multiply the normalized value obtained from the curves in Figs. 3,
4, 5 or 6 by the value indicated on the power loss curve in Fig. 1. If multiple adjustments are required, multiply all of the
normalized values together, then multiply that product by the value indicated on the power loss curve in Fig. 1. The resulting
product is the final power loss based on all factors. See example no. 1.
To make adjustments to the SOA curve in Fig. 2, determine your maximum PCB Temp & Case Temp at the maximum operating
current of each iP2002PbF. Then, add the correction temperature from the normalized curves in Figs. 3, 4, 5 or 6 to the T
X
axis
intercept (see procedure no. 2 above) in Fig. 2. When multiple adjustments are required, add all of the temperatures
together, then add the sum to the T
X
axis intercept in Fig. 2. See example no. 2.
Operating Conditions for the following examples:
Output Current = 30A Input Voltage = 10V Output Voltage = 3.3V
Sw Freq= 900kHz Inductor = 0.2uH
Example 1) Adjusting for Maximum Power Loss:
(Fig. 1) Maximum power loss = 11W
(Fig. 3) Normalized power loss for input voltage ≈ 0.98
(Fig. 4) Normalized power loss for output voltage ≈ 1.28
(Fig. 5) Normalized power loss for frequency ≈ 0.955
(Fig. 6) Normalized power loss for inductor value ≈ 1.02
Adjusted Power Loss = 11W x 0.98 x 1.28 x 0.955 x 1.02 ≈ 13.44W
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.
Procedure
1) Draw a line from Case Temp axis at T
CASE
to the PCB
Temp axis at T
PCB
.
2) Draw a vertical line from the T
X
axis intercept to the SOA
curve.
3) Draw a horizontal line from the intersection of the vertical
line with the SOA curve to the Y axis. The point at which
the horizontal line meets the y-axis is the SOA current.
0 102030405060708090100110120
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
0 102030405060708090100110120
PCB Temperature (ºC)
Output Current (A)
Safe
Operating
Area
V
IN
= 12V
V
OUT
= 1.3V
f
SW
= 1MHz
L = 0.30uH
Case Temperature (
T
X
1
2
3
