8.2.2 Detailed Design Procedures

8.2.2.1 Custom Design With WEBENCH® Tools

Click here to create a custom design using the TPS54622-EP device with the WEBENCH® Power Designer.

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.

8.2.2.2 Operating Frequency

The first step is to decide on a switching frequency for the regulator. There is a trade off between higher and

lower switching frequencies. Higher switching frequencies may produce smaller a solution size using lower

valued inductors and smaller output capacitors compared to a power supply that switches at a lower frequency.

However, the higher switching frequency causes extra switching losses, which hurt the converter’s efficiency and

thermal performance. In this design, a moderate switching frequency of 480 kHz is selected to achieve both a

small solution size and a high-efficiency operation.

8.2.2.3 Output Inductor Selection

To calculate the value of the output inductor, use Equation 18. KIND is a coefficient that represents the amount

of inductor ripple current relative to the maximum output current. The inductor ripple current is filtered by the

output capacitor. Therefore, choosing high inductor ripple currents impact the selection of the output capacitor

since the output capacitor must have a ripple current rating equal to or greater than the inductor ripple current. In

general, the inductor ripple value is at the discretion of the designer; however, KIND is normally from 0.1 to 0.3

for the majority of applications.

f

-

=

×

×

×

Vinm ax

Vout

Vout

L1

Io Kind

Vinm ax

sw

(18)

For this design example, use KIND = 0.3 and the inductor value is calculated to be 3.08 µH. For this design, a

nearest standard value was chosen: 3.3 µH. For the output filter inductor, it is important that the RMS current

and saturation current ratings not be exceeded. The RMS and peak inductor current can be found from Equation

20 and Equation 21.

f

-

=

×

×

Vinmax

Vout

Vout

Iripple

L1

Vinmax

sw

(19)

(

)

2

2

1

12

f

æ

ö

×

-

=

+

×ç

÷

ç

÷

×

×

è

ø

o

V

Vinmax

Vo

ILrms

Io

Vinmax L1

sw

(20)

2

=

+

Iripple

ILpeak

Iout

(21)

TPS54622-EP

SLVSFN6 – DECEMBER 2020

www.ti.com

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