8.2.2 Detailed Design Procedure

8.2.2.1 Custom Design with WEBENCH® Tools

Click here to create a custom design using the TPSM861253 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.

8.2.2.2 Output Filter Selection

TPSM861253 integrates a 2.2uH inductor and divider resistor. TI suggests to use below output cap to make loop

stable. VOS pin is suggested to connect to output voltage directly.

Table 8-2. Recommended Component Values

Output Voltage (V)

Minimum COUT (μF)

Typical COUT (μF)

Maximum COUT (μF)

3.3

22

22

100

The capacitor value and ESR determines the amount of output voltage ripple. The TPSM861253 are intended for

use with ceramic or other low-ESR capacitors. Use Equation 1 to determine the required RMS current rating for

the output capacitor.

ILORMS = IO2+ 112×IIP−P2

(1)

For this design, one MuRata GRM21BR61A226ME44L 22µF output capacitor is used. The typical ESR is 2mΩ

each.

8.2.2.3 Input Capacitor Selection

The TPSM861253 requires an input decoupling capacitor and a bulk capacitor is needed depending on the

application. TI recommends a ceramic capacitor over 10µF for the decoupling capacitor. TI recommends an

additional 0.1µF capacitor from the VIN pin to ground to provide high frequency filtering. The capacitor voltage

rating must be greater than the maximum input voltage.

8.2.2.4 Enable Circuit

The EN pin controls the turn-on and turn-off of the device. When EN pin voltage is above the turn-on threshold,

the device starts switching and when the EN pin voltage falls below the turn-off threshold IC stops switching. The

default status is low. There is a 2MΩ internal pulldown resistor in the EN pin.

EN can be controlled by a typical divider resistor circuit from Vin or by a voltage of lower than 5.5V.

Because there is a 2MΩ internal pulldown resistor in the EN pin, TPSM861253 also supports to only connect

a top resistor from VIN pin to EN pin. EN voltage is got by the divide net of top resistor and 2MΩ. EN voltage

cannot be allowed to be over 6V.

www.ti.com

TPSM861253

SLUSFD2A – SEPTEMBER 2023 – REVISED JANUARY 2024

Copyright © 2024 Texas Instruments Incorporated

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Product Folder Links: TPSM861253