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04/09/2009

8

iP2005CPbF

PD-60360

Calculating Power Loss and SOA for Different Operating Conditions

To calculate Power Loss for a given set of operation conditions, the following procedure should be

followed:

Power Loss Procedure

1. Determine the maximum current and obtain the maximum power loss from figure 1

2. Use the normalized curves to obtain power loss values that match the operating conditions in

the application

3. The maximum power loss under the application conditions is then the product of the power

loss from figure 1and the normalized values.

To calculate the Safe Operating Area (SOA) for a given set of operating conditions, the following

procedure should be followed:

SOA Procedure

1. Determine the maximum PCB and CASE temperature at the maximum operating current for

each iP2005C

2. Use the normalized curves to obtain SOA temperature adjustments that match the operating

conditions in the application

Design Example

Operating Conditions

:

Output Current = 30A

Input Voltage = 10V

Output Voltage = 1.3V

Switching Freq = 750 kHz

Inductor = 0.2µH

Drive Voltage (VDD) = 5V

Calculating Maximum Power Loss:

(Figure 1) Maximum power loss = 7.0W

(Figure 3) Normalized power loss for input voltage

≈ 0.975

(Figure 5) Normalized power loss for output inductor

≈ 1.012

(Figure 6) Normalized power loss for switch frequency

≈ 0.88

Calculated Maximum Power Loss

≈ 7.0W x 0.975 x 1.0 x 1.012 x 0.88 ≈ 6.09W