ZHCSNB4 february 2023 LM5148
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 Dual Random Spread Spectrum (DRSS)
- 8.3.7 Soft Start
- 8.3.8 Output Voltage Setpoint (FB)
- 8.3.9 Minimum Controllable On Time
- 8.3.10 Error Amplifier and PWM Comparator (FB, EXTCOMP)
- 8.3.11 Slope Compensation
- 8.3.12 Inductor Current Sense (ISNS+, VOUT)
- 8.3.13 Hiccup Mode Current Limiting
- 8.3.14 High-Side and Low-Side Gate Drivers (HO, LO)
- 8.3.15 Output Configurations (CNFG)
- 8.3.16 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
- 9.2.1.3 Application Curves
- 9.2.2 Design 2 – High Efficiency 48-V to 12-V 400-kHz Synchronous Buck Regulator
- 9.2.3 Design 3 – High Efficiency 440-kHz Synchronous Buck Regulator
- 9.2.4 Design 4 – Dual-Phase 400-kHz 20-A Synchronous Buck Regulator
- 9.2.1
Design 1 – High Efficiency 2.1-MHz Synchronous
Buck Regulator
- 9.3 Power Supply Recommendations
- 9.4 Layout
- 10Device and Documentation Support
- 11Mechanical, Packaging, and Orderable Information
8.3.5 Switching Frequency (RT)
Program the LM5148 oscillator with a resistor from RT to AGND to set an oscillator frequency from 100 kHz and 2.2 MHz. Calculate the RT resistance for a given switching frequency using Equation 4.
Under low VIN conditions when the on time of the high-side MOSFET exceeds the programmed oscillator period, the LM5148 extends the switching period until the PWM latch is reset by the current sense ramp exceeding the controller compensation voltage.
The approximate input voltage level at which this occurs is given by Equation 5.
where
- tSW is the switching period.
- tOFF(min) is the minimum off time of 90 ns.