ZHCSLO5B December 2020 – December 2021 LM25149
PRODUCTION DATA
- 1 特性
- 2 应用
- 3 说明
- 4 Revision History
- 5 说明（续）
- 6 Pin Configuration and Functions
- 7 Specifications
-
8 Detailed Description
- 8.1 Overview
- 8.2 Functional Block Diagram
- 8.3
Feature Description
- 8.3.1 Input Voltage Range (VIN)
- 8.3.2 High-Voltage Bias Supply Regulator (VCC, VCCX, VDDA)
- 8.3.3 Precision Enable (EN)
- 8.3.4 Power-Good Monitor (PG)
- 8.3.5 Switching Frequency (RT)
- 8.3.6 Active EMI Filter
- 8.3.7 Dual Random Spread Spectrum (DRSS)
- 8.3.8 Soft Start
- 8.3.9 Output Voltage Setpoint (FB)
- 8.3.10 Minimum Controllable On Time
- 8.3.11 Error Amplifier and PWM Comparator (FB, EXTCOMP)
- 8.3.12 Slope Compensation
- 8.3.13 Inductor Current Sense (ISNS+, VOUT)
- 8.3.14 Hiccup Mode Current Limiting
- 8.3.15 High-Side and Low-Side Gate Drivers (HO, LO)
- 8.3.16 Output Configurations (CNFG)
- 8.3.17 Single-Output Dual-Phase Operation
- 8.4 Device Functional Modes
-
9 Application and Implementation
- 9.1 Application Information
- 9.2
Typical Applications
- 9.2.1
Design 1 – High Efficiency 2.1-MHz Synchronous
Buck Regulator
- 9.2.1.1 Design Requirements
- 9.2.1.2
Detailed Design Procedure
- 9.2.1.2.1 Custom Design With WEBENCH® Tools
- 9.2.1.2.2 Custom Design With Excel Quickstart Tool
- 9.2.1.2.3 Buck Inductor
- 9.2.1.2.4 Current-Sense Resistance
- 9.2.1.2.5 Output Capacitors
- 9.2.1.2.6 Input Capacitors
- 9.2.1.2.7 Frequency Set Resistor
- 9.2.1.2.8 Feedback Resistors
- 9.2.1.2.9 Compensation Components
- 9.2.1.2.10 Active EMI Components
- 9.2.1.3 Application Curves
- 9.2.2 Design 2 – High Efficiency 440-kHz Synchronous Buck Regulator
- 9.2.3 Design 3 – Dual-Phase 400-kHz 20-A Synchronous Buck Regulator
- 9.2.1
Design 1 – High Efficiency 2.1-MHz Synchronous
Buck Regulator
- 10Power Supply Recommendations
- 11Layout
- 12Device and Documentation Support
- 13Mechanical, Packaging, and Orderable Information
9.2.1.2.3 Buck Inductor
- Use Equation 33 to calculate the required buck inductance based on a 30% inductor ripple current at
nominal input voltages. Equation 33.
- Select a standard inductor value of 0.56 µH or
use a 0.68 µH to account for effective inductance derating with current of molded
inductors. Use Equation 34 to calculate the peak inductor current at maximum steady-state input voltage.
Subharmonic oscillation occurs with a duty cycle greater than 50% for peak current-mode
control. For design simplification, the LM25149 has an internal slope compensation ramp proportional to the switching
frequency that is added to the current sense signal to damp any tendency toward
subharmonic oscillation. Equation 34.
- Based on Equation 8, use Equation 35 to cross-check the inductance to set a slope compensation close to the ideal one times
the inductor current downslope.Equation 35.
