SLVSFP4B August   2020  – March 2021

PRODUCTION DATA

1. Features
2. Applications
3. Description
4. Revision History
5. Pin Configuration and Functions
6. Specifications
7. Detailed Description
1. 7.1 Overview
2. 7.2 Functional Block Diagram
3. 7.3 Feature Description
4. 7.4 Device Functional Modes
8. Application and Implementation
1. 8.1 Application Information
2. 8.2 Typical Applications
1. 8.2.1 Design Requirements
2. 8.2.2 Detailed Design Procedure
3. 8.2.3 Application Curves
9. Power Supply Recommendations
10. 10Layout
11. 11Device and Documentation Support
12. 12Mechanical, Packaging, and Orderable Information

#### Package Options

• RPU|10
##### 8.2.2.2.2 Inductor Selection for the First L-C Filter

The inductor selection is dependent on the selected switching frequency and the duty cycle. When using the 2.2-MHz frequency, only use a 2.2-µH inductor. When using the 1-MHz frequency, calculate the maximum duty cycle using the minimum input voltage. If Dmax is above 45%, only use a 4.7-µH inductor. If Dmax is below 45% and the output voltage is 2 V or less, use only a 2.2-µH inductor. If Dmax is below 45% and the output voltage is above 2 V, use a 4.7-µH inductor to achieve the full output current or a 2.2-µH inductor for higher efficiency with a reduced maximum output current.

The inductor also has to be rated for the appropriate saturation current. Equation 5 and Equation 6 calculate the maximum inductor current under static load conditions. The formula takes the converter efficiency into account. The calculation must be done for the maximum input voltage where the peak switch current is highest.

Equation 6.
Equation 6.

where

• ƒSW is the switching frequency (typically 1 MHz or 2.2 MHz)
• L is inductance
• η is estimated efficiency (use the value from the efficiency curves or 0.9 as an conservative assumption)
Note: The calculation must be done for the maximum input voltage of the application.

Calculating the maximum inductor current using the actual operating conditions gives the minimum saturation current. A margin of 20% is recommended to be added to cover for load transients during operation.

See Table 8-4 for typical inductors.

Table 8-4 Inductor Selection
INDUCTOR VALUEMANUFACTURERPART NUMBERSIZE (L X W X H IN mm)ISAT/DCR (30% DROP)
2.2 µHCoilcraft XGL4020-2224 × 4 × 2.16.2 A / 19.5 mΩ
2.2 µHCoilcraft XGL4030-2224 × 4 × 3.17 A / 13.5 mΩ
2.2 µHWurth Elektronik744383560224.1 × 4.1 × 2.15.2 A / 35 mΩ
2.2 µHWurth Elektronik744383570224.1 × 4.1 × 3.17 A / 26 mΩ
2.2 µHMuRataDFE322520FD-2R2M=P23.2 × 2.5 × 25 A / 46 mΩ
4.7 µHCoilcraft XGL4020-4724 × 4 × 2.14.1 A / 43.0 mΩ
4.7 µHCoilcraft XGL4030-4724 × 4 × 3.14.4 A / 28.5 mΩ
4.7 µH for TPS62912 onlyMuRataDFE322520FD-4R7M=P23.2 × 2.5 × 23.4 A / 98 mΩ