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CSD87331Q3D

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SLPS283B – SEPTEMBER 2011 – REVISED FEBRUARY 2017

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Copyright © 2011–2017, Texas Instruments Incorporated

6.2 Typical Application

Figure 32. Typical Application

6.2.1 Calculating Power Loss and SOA

The user can estimate product loss and SOA boundaries by arithmetic means (see Design Example section).

Though the power loss and SOA curves in this data sheet are taken for a specific set of test conditions, the

following procedure will outline the steps the user should take to predict product performance for any set of

system conditions.

6.2.1.1 Design Example

Operating conditions:

•

Output current = 10 A

•

Input voltage = 10 V

•

Output voltage = 1 V

•

Switching frequency = 1000 kHz

•

Inductor = 0.4 µH

6.2.1.2 Calculating Power Loss

•

Power loss at 10 A = 1.8 W (Figure 1)

•

Normalized power loss for input voltage

≈ 1 (Figure 7)

•

Normalized power loss for output voltage

≈ 0.95 (Figure 8)

•

Normalized power loss for switching frequency

≈ 1.15 (Figure 6)

•

Normalized power loss for output inductor

≈ 1.04 (Figure 9)

•

Final calculated power loss = 1.8 W × 1.0 × 0.95 × 1.15 × 1.04

≈ 2.05 W

6.2.1.3 Calculating SOA Adjustments

•

SOA adjustment for input voltage

≈ 0.1°C (Figure 7)

•

SOA adjustment for output voltage

≈ –1.3°C (Figure 8)

•

SOA adjustment for switching frequency

≈ 4.2°C (Figure 6)

•

SOA adjustment for output inductor

≈ 1°C (Figure 9)

•

Final calculated SOA adjustment = 0.1 + (–1.3) + 4.2 + 1

≈ 4.8°C