LM5145 datasheet(41/73 Pages) TI2

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8.2.1.2 Detailed Design Procedure

8.2.1.2.1 Custom Design With WEBENCH® Tools

Click here to create a custom design using the LM25137 device with the WEBENCH® Power Designer.

1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.

2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.

3. Compare the generated design with other possible solutions from Texas Instruments.

The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time

pricing and component availability.

In most cases, these actions are available:

• Run electrical simulations to see important waveforms and circuit performance

• Run thermal simulations to understand board thermal performance

• Export customized schematic and layout into popular CAD formats

• Print PDF reports for the design, and share the design with colleagues

Get more information about WEBENCH tools at www.ti.com/WEBENCH.

8.2.1.2.2 Custom Design With Excel Quickstart Tool

Select components based on the regulator specifications using the LM25137 Quickstart Calculator available for

download from the LM25137 product folder.

8.2.1.2.3 Inductor Calculations

1. Use Equation 29 to calculate the required buck inductance for each channel based on an approximate 30%

inductor peak-to-peak ripple current at nominal input voltage.

(29)

2. Select a standard inductor value of 1µH for both channels. Use Equation 30 to calculate the peak inductor

currents at maximum steady-state input voltage. Subharmonic oscillation occurs with a duty cycle greater

than 50% for peak current-mode control. For design simplification, the LM25137 has an internal slope

compensation ramp proportional to the switching frequency that is added to the current sense signal to damp

any tendency toward subharmonic oscillation.

(30)

3. Based on Equation 29, use Equation 31 to cross-check the inductances to align the slope compensation

ramp to an ideal one times the inductor current downslope.

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LM5145 Datasheet(PDF) 41 Page - Texas Instruments