SNVS690I January   2011  – August 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 Application
1. 8.2.1 Design Requirements
2. 8.2.2 Detailed Design Procedure
1. 8.2.2.1 Design Steps for the LMZ14201H Application
3. 8.2.3 Application Curve
9. Power Supply Recommendations
10. 10Layout
1. 10.1 Layout Guidelines
2. 10.2 Layout Example
11. 11Device and Documentation Support
12. 12Mechanical, Packaging, and Orderable Information

Package Options

• NDW|7
Orderable Information
8.2.2.1.6.1 Discontinuous Conduction and Continuous Conduction Mode Selection

Operating frequency in DCM can be calculated as follows:

Equation 17. fSW(DCM) ≊ VO × (VIN-1) × 15 μH × 1.18 × 1020 × IO / ((VIN–VO) × RON2)

In CCM, current flows through the inductor through the entire switching cycle and never falls to zero during the OFF-time. The switching frequency remains relatively constant with load current and line voltage variations. The CCM operating frequency can be calculated using Equation 12 above.

The approximate formula for determining the DCM/CCM boundary is as follows:

Equation 18. IDCB ≊ VO × (VIN–VO) / ( 2 × 15 μH × fSW(CCM) × VIN)

The inductor internal to the module is 15 μH. This value was chosen as a good balance between low and high input voltage applications. The main parameter affected by the inductor is the amplitude of the inductor ripple current (ILR). ILR can be calculated with:

Equation 19. ILR P-P = VO × (VIN- VO) / (15 µH × fSW × VIN)

where

• VIN is the maximum input voltage and fSW is determined from Equation 12.

If the output current IO is determined by assuming that IO = IL, the higher and lower peak of ILR can be determined. Be aware that the lower peak of ILR must be positive if CCM operation is required.