SNVSCU3 October 2025 LM5137
PRODMIX
- 1
- 1 Features
- 2 Applications
- 3 Description
- 4 Related Products
- 5 Pin Configuration and Functions
- 6 Specifications
-
7 Detailed Description
- 7.1 Overview
- 7.2 Functional Block Diagram
- 7.3
Feature Description
- 7.3.1 Input Voltage Range (VIN)
- 7.3.2 Bias Supply Regulator (VCC, BIAS1/VOUT1, VDDA)
- 7.3.3 Precision Enable (EN1, EN2)
- 7.3.4 Switching Frequency (RT)
- 7.3.5 Pulse Frequency Modulation and Synchronization (PFM/SYNC)
- 7.3.6 Synchronization Out (SYNCOUT)
- 7.3.7 Dual Random Spread Spectrum (DRSS)
- 7.3.8 Configurable Soft Start (RSS)
- 7.3.9 Output Voltage Setpoints (FB1, FB2)
- 7.3.10 Error Amplifier and PWM Comparator (FB1, FB2, COMP1, COMP2)
- 7.3.11 Inductor Current Sense (ISNS1+, BIAS1/VOUT1, ISNS2+, VOUT2)
- 7.3.12 Minimum Controllable On-Time
- 7.3.13 100% Duty Cycle Capability
- 7.3.14 MOSFET Gate Drivers (HO1, HO2, LO1, LO2)
- 7.3.15 Output Configurations (CNFG)
- 7.4 Device Functional Modes
-
8 Application and Implementation
- 8.1 Application Information
- 8.2
Typical Applications
- 8.2.1
Design 1 – Dual 5V and 3.3V, 20A Buck Regulator for 12V
Input Applications
- 8.2.1.1 Design Requirements
- 8.2.1.2
Detailed Design Procedure
- 8.2.1.2.1 Custom Design With WEBENCH? Tools
- 8.2.1.2.2 Custom Design With Excel Quickstart Tool
- 8.2.1.2.3 Inductor Calculations
- 8.2.1.2.4 Shunt Resistors
- 8.2.1.2.5 Ceramic Output Capacitors
- 8.2.1.2.6 Ceramic Input Capacitors
- 8.2.1.2.7 Feedback Resistors
- 8.2.1.2.8 Input Voltage UVLO Resistors
- 8.2.1.2.9 Compensation Components
- 8.2.1.3 Application Curves
- 8.2.2 Design 2 – Two-Phase, Single-Output Synchronous Buck Regulator
- 8.2.3 Design 3 – 12V, 20A, 400kHz, Two-Phase Buck Regulator for 48V Server Applications
- 8.2.1
Design 1 – Dual 5V and 3.3V, 20A Buck Regulator for 12V
Input Applications
- 8.3 Power Supply Recommendations
- 8.4 Layout
- 9 Device and Documentation Support
- 10Revision History
- 11Mechanical, Packaging, and Orderable Information
封裝選項
機械數(shù)據(jù) (封裝 | 引腳)
- RHA|36
散熱焊盤機械數(shù)據(jù) (封裝 | 引腳)
- RHA|36
訂購信息
7.3.12 Minimum Controllable On-Time
There are two limitations to the minimum output voltage adjustment range: the LM5137 voltage reference of 0.8V and the minimum controllable switch-node pulse width, tON(min).
tON(min) effectively limits the voltage step-down conversion ratio of VOUT/VIN at a given switching frequency. For fixed-frequency PWM operation, the voltage conversion ratio must satisfy Equation 8.
where
- tON(min) is 22ns (typical)
- FSW is the switching frequency
If the desired voltage conversion ratio does not meet the above condition, the LM5137 transitions from fixed switching frequency operation to a pulse-skipping mode to maintain output voltage regulation. For example, if the desired output voltage is 1.2V with an input voltage is 24V and switching frequency of 2.1MHz, the voltage conversion ratio test in Equation 9 is satisfied.
For wide VIN applications and low output voltages, an alternative is to reduce the LM5137 switching frequency to meet the requirement of Equation 8.