TPS62933O datasheet(25/47 Pages) TI

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9.2.2 Detailed Design Procedure

9.2.2.1 Custom Design With WEBENCH® Tools

To create a custom design using the TPS62933 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.

9.2.2.2 Output Voltage Resistors Selection

The output voltage is set with a resistor divider from the output node to the FB pin. TI recommends using 1%

tolerance or better divider resistors. Referring to the application schematic of Figure 9-1, start with 10.2 kΩ for

R7 and use Equation 14 to calculate R6 = 53.6 kΩ. To improve efficiency at light loads, consider using larger

value resistors. If the values are too high, the converter is more susceptible to noise and voltage errors from the

FB input leakage current are noticeable.

OUT

REF

(14)

Table 9-2 shows the recommended components value for common output voltages.

9.2.2.3 Choosing Switching Frequency

The choice of switching frequency is a compromise between conversion efficiency and overall solution size.

Higher switching frequency allows the use of smaller inductors and output capacitors, and hence, a more

compact design. However, lower switching frequency implies reduced switching losses and usually results in

higher system efficiency, so the 500-kHz switching frequency was chosen for this example, remove the jumper

on JP2 and leave RT pin floating.

Please note the switching frequency is also limited by the following as mentioned in Section 8.3.8:

• Minimum on time of the integrated power switch

• Input voltage

• Output voltage

• Frequency shift limitation

9.2.2.4 Soft-Start Capacitor Selection

The large CSS can reduce inrush current when driving large capacitive load, here chooses 33 nF for C4 which

sets the soft start time tSS to approximately 5 mS.

In addition, the SS pin cannot be floated, a minimum 6.8-nF capacitor must be connected at this pin.

9.2.2.5 Bootstrap Capacitor Selection

A 0.1-µF ceramic capacitor must be connected between the BST to SW pins for proper operation. TI

recommends to use a ceramic capacitor with X5R or better grade dielectric. The capacitor C5 must have a

16-V or higher voltage rating.

www.ti.com

TPS62933

SLUSEA4A – JUNE 2021 – REVISED DECEMBER 2021

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