SLVSB64I November   2011  – March 2018

PRODUCTION DATA.

1. Features
2. Applications
3. Description
1.     Device Images
4. Revision History
5. Device Comparison Table
6. Pin Configuration and Functions
7. Specifications
8. Detailed Description
1. 8.1 Overview
2. 8.2 Functional Block Diagram
3. 8.3 Feature Description
4. 8.4 Device Functional Modes
1. 8.4.1 PMIC States
5. 8.5 Programming
6. 8.6 Register Maps
9. Application and Implementation
1. 9.1 Application Information
2. 9.2 Typical Application
1. 9.2.1 Design Requirements
2. 9.2.2 Detailed Design Procedure
3. 9.2.3 Application Curves
10. 10Power Supply Recommendations
11. 11Layout
12. 12Device and Documentation Support
13. 13Mechanical, Packaging, and Orderable Information

• RSL|48
• RSL|48

#### 9.2.2.1.1 Inductor Selection for Buck Converters

The step-down converters operate typically with 2.2-µH output inductors. Larger or smaller inductor values can be used to optimize the performance of the device for specific operation conditions. The selected inductor must be rated for its dc resistance and saturation current. The dc resistance of the inductance directly influences the efficiency of the converter. Therefore, an inductor with the lowest dc resistance should be selected for highest efficiency.

Use Equation 4 to calculate the maximum inductor current under static load conditions. The saturation current of the inductor should be rated higher than the maximum inductor current, because, during heavy load transients, the inductor current increases to a value greater than the calculated value.

Equation 4.

where

• ILmax is the maximum inductor current
• IOUTmax is the maximum output current
• ΔIL is the peak-to-peak inductor ripple current (see Equation 5)
Equation 5.

where

• L is the inductor value.
• f is the switching frequency (2.25 MHz typical).

The highest inductor current occurs at maximum input voltage (VIN). Open-core inductors have a soft saturation characteristic and can usually support greater inductor currents than a comparable shielded inductor.

A more conservative approach is to select the inductor current rating just for the maximum switch current of the corresponding converter. The core material must be considered because it differs from inductor to inductor and has an impact on the efficiency, especially at high switching frequencies. Also, the resistance of the windings greatly affects the converter efficiency at high load. Table 35 lists the recommended inductors.

### Table 35. Recommended Inductors for DCDC1, DCDC2, and DCDC3

PART NUMBER SUPPLIER VALUE (µH) RDS (mΩ) MAX RATED CURRENT (A) DIMENSIONS (mm)
LQM2HPN2R2MG0L Murata 2.2 100 1.3 2 x 2.5 x 0.9
VLCF4018T-2R2N1R4-2 TDK 2.2 60 1.44 3.9 x 4.7 x 1.8