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LM5161

ACTIVE

Wide Input 4.5-V to 100-V, 1-A Synchronous Buck / Fly-Buck Converter

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Data sheet

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LM5164 ACTIVE 6-V to 100-V input, 1-A synchronous buck DC-DC converter with ultra-low IQ Ultra-low EMI emission.

LM5161

ACTIVE
Data sheet Order now

Product details

Rating Catalog Topology Buck, Flybuck Iout (max) (A) 1 Vin (max) (V) 100 Vin (min) (V) 4.5 Vout (max) (V) 92 Vout (min) (V) 2 Switch current limit (typ) (A) 1.6 Features Enable, Light load efficiency, Pre-bias soft start, Synchronous rectification Control mode COT with emulated ripple, Constant on-time (COT) Operating temperature range (°C) -40 to 125 Iq (typ) (A) 0.00005 Duty cycle (max) (%) 92
Rating Catalog Topology Buck, Flybuck Iout (max) (A) 1 Vin (max) (V) 100 Vin (min) (V) 4.5 Vout (max) (V) 92 Vout (min) (V) 2 Switch current limit (typ) (A) 1.6 Features Enable, Light load efficiency, Pre-bias soft start, Synchronous rectification Control mode COT with emulated ripple, Constant on-time (COT) Operating temperature range (°C) -40 to 125 Iq (typ) (A) 0.00005 Duty cycle (max) (%) 92
HTSSOP (PWP) 14 32 mm² (5 mm × 6.4 mm)
  • Wide 4.5-V to 100-V Input Voltage Range
  • Integrated High-Side and Low-Side Switches
    • No Schottky Diode Required
  • 1-A Maximum Load Current
  • Constant ON-Time Control
    • No External Loop Compensation
    • Fast Transient Response
  • Selectable DCM Buck Operation at Light Load
  • CCM Option Supports Multi-Output Fly-Buck™
  • No External Ripple circuit needed (at FPWM = 0)
  • Nearly Constant Switching Frequency
  • Frequency Adjustable Up to 1 MHz
  • Programmable Soft-Start Time
  • Prebias Start-Up
  • Peak Current Limiting Protection
  • Adjustable Input UVLO and Hysteresis
  • ±1% Feedback Voltage Reference
  • Thermal Shutdown Protection
  • Create a Custom Design Using the LM5161 With the WEBENCH® Power Designer
  • Wide 4.5-V to 100-V Input Voltage Range
  • Integrated High-Side and Low-Side Switches
    • No Schottky Diode Required
  • 1-A Maximum Load Current
  • Constant ON-Time Control
    • No External Loop Compensation
    • Fast Transient Response
  • Selectable DCM Buck Operation at Light Load
  • CCM Option Supports Multi-Output Fly-Buck™
  • No External Ripple circuit needed (at FPWM = 0)
  • Nearly Constant Switching Frequency
  • Frequency Adjustable Up to 1 MHz
  • Programmable Soft-Start Time
  • Prebias Start-Up
  • Peak Current Limiting Protection
  • Adjustable Input UVLO and Hysteresis
  • ±1% Feedback Voltage Reference
  • Thermal Shutdown Protection
  • Create a Custom Design Using the LM5161 With the WEBENCH® Power Designer

The LM5161 is a 100-V, 1-A synchronous step-down converter with integrated high-side and low-side MOSFETs. The constant-ON-time control scheme requires no loop compensation and supports high step-down ratios with fast transient response. An internal feedback amplifier maintains ±1% output voltage regulation over the entire operating temperature range. The ON-time varies inversely with input voltage resulting in nearly constant switching frequency. Peak and valley current limit circuits protect against overload conditions. The under-voltage lockout (EN/UVLO) circuit provides independently adjustable input undervoltage threshold and hysteresis. The FPWM input pin in LM5161 selects either the forced continuous conduction mode (CCM) under all load levels or the discontinuous conduction mode (DCM) under light or no load conditions. When operating in forced CCM, the LM5161 supports the multiple output and isolated Fly-Buck applications. When programmed for the DCM operation, the LM5161 provides a tightly regulated buck output without any additional external feedback ripple injection circuit.

The LM5161 is a 100-V, 1-A synchronous step-down converter with integrated high-side and low-side MOSFETs. The constant-ON-time control scheme requires no loop compensation and supports high step-down ratios with fast transient response. An internal feedback amplifier maintains ±1% output voltage regulation over the entire operating temperature range. The ON-time varies inversely with input voltage resulting in nearly constant switching frequency. Peak and valley current limit circuits protect against overload conditions. The under-voltage lockout (EN/UVLO) circuit provides independently adjustable input undervoltage threshold and hysteresis. The FPWM input pin in LM5161 selects either the forced continuous conduction mode (CCM) under all load levels or the discontinuous conduction mode (DCM) under light or no load conditions. When operating in forced CCM, the LM5161 supports the multiple output and isolated Fly-Buck applications. When programmed for the DCM operation, the LM5161 provides a tightly regulated buck output without any additional external feedback ripple injection circuit.
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Technical documentation

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Top documentation Type Title Format options Date
* Data sheet LM5161 Wide Input 100-V, 1-A Synchronous Buck/Fly-Buck™ Converter datasheet (Rev. B) PDF | HTML Nov 27, 2017
Product overview Isolated Power Topologies for PLC I/O Modules and Other Low-Power Applications (Rev. A) PDF | HTML Aug 20, 2024
Application note Step-Dwn (Buck) Convrtr Pwer Solutions for Programmable Logic Controller Systems (Rev. A) PDF | HTML Jul 26, 2021
Selection guide Buck Converter Quick Reference Guide (Rev. B) Apr 8, 2021
White paper Valuing wide VIN, low EMI synchronous buck circuits for cost-driven, demanding a (Rev. A) Apr 10, 2019
Application note Stability Analysis and Design of COT Type-3 Ripple Circuit Mar 20, 2019
Application brief Powering Drones With a Wide VIN DC-DC Converter (Rev. A) Feb 5, 2019
Technical article Why a wide VIN DC/DC converter is a good fit for high-cell-count battery-powered d PDF | HTML Nov 21, 2017
Technical article Simplifying 100V wide VIN power conversion PDF | HTML Nov 11, 2016
Technical article Create a Fly-Buck™ converter in WEBENCH® Power Designer PDF | HTML Oct 9, 2015
White paper Designing isolated rails on the fly with Fly-Buck™ converters Sep 29, 2015
Technical article How to design for EMC and isolation with Fly-Buck™ converters PDF | HTML Jul 28, 2015
Application note Is Your IGBT Gate-Driver Power Supply Optimized Mar 12, 2015
Analog design Journal Fly-Buck(TM) converter provides EMC and isolation in PLC applications Jan 29, 2015
Application note AN-2292 Designing an Isolated Buck (Fly-Buck) Converter (Rev. C) Dec 17, 2014
White paper Wide VIN power management ICs simplify white paper (Rev. A) Sep 19, 2013
Application note AN-2218 Precision Current Limiting with the LMP8646 and LM3102 (Rev. A) Apr 23, 2013

Design & development

For additional terms or required resources, click any title below to view the detail page where available.

Evaluation board

LM5161PWPBKEVM — LM5161 Wide VIN Synchronous Buck Converter Constant On-Time Evaluation Module

The LM5161PWPBKEVM evaluation board provides a fully functional buck regulator, employing the constant on-time (COT) operating principle. This evaluation board provides a 12-V output over an input range of 15V to 80 V. The circuit delivers load currents to 1.0 A. The application schematic is setup (...)
User guide: PDF
Supported products & hardware
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Evaluation board

LM5161PWPFBKEVM — LM5161 Wide VIN Fly-Buck Evaluation Module

The LM5161PWPFBKEVM evaluation board provides a fully functional Fly-buck regulator, employing the constant on-time (COT) operating principle. This evaluation board provides a 12-V secondary isolated output voltage over an input range of 36V to 72 V. The circuit delivers secondary output load (...)
User guide: PDF
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Simulation model

LM5161 PSpice Buck and Fly-Buck Transient Model

SNVMAV3.ZIP (499 KB) - PSpice model
Supported products & hardware
Simulation model

LM5161 Unencrypted PSpice Buck and Fly-Buck Transient Model

SNVMAV4.ZIP (3 KB) - PSpice model
Supported products & hardware
Calculation tool

FLYBUCK-FLYBACK-DESIGN-CALC — Flybuck / Flyback Calculator

This tool helps a power supply engineer to select the right isolated DC-DC topology based on the specifications. Depending on the topology chosen, the calculator also recommends the right IC for the design.

Supported products & hardware
Calculation tool

SNVC199 — LM5161 Buck Quick Start Component Selector

Supported products & hardware
Calculation tool

SNVC200 — LM5161 Fly-Buck Quick Start Component Selector

Supported products & hardware
Reference design

PMP20587 — Inverting buck-boost reference design

This reference design uses UCD3138064A as a digital controller to control two-phase two-rail inverting buck-boost. This non-isolated converter is used for wireless radio power. The input voltage is from -35 V to -60 V. There are two outputs. The default output voltage of rail 1 is 32 V and max (...)
Supported products & hardware
Reference design

PMP23332 — Interleaved and multiphase inverting buck-boost converter reference design

This reference design uses the UCD3138064A as a digital controller to control inverting buck-boost with the capability of supporting two-phase peak current mode control. The soft-switching technology is used in this design to improve the power efficiency. The input voltage range is -62 V to -36 V. (...)

Supported products & hardware
Reference design

PMP40042 — Flybuck For 48Vin Isolated System Aux. Power Reference Design

The PMP40042 is a D-CAP Aux. isolated power supply reference design solution for the Telecom & Server applications. High integration and low switching loss, with the UVLO, OTP, OCP, SS and Prebias Start-up, the module enables a high efficiency for 48V system application.  A low cost & (...)
Supported products & hardware
Reference design

PMP4486 — 48Vin Digital POL with 3 Outputs Reference Design

The PMP4486 is a GaN-based reference design solution for telecom and computing applications. The GaN module LMG5200 enables a high efficiency single stage conversion with an input range from 36 to 60V down to 29V, 12V and 1.0V. This design shows the benefits of a GaN based design with high (...)
Supported products & hardware
Package Pins CAD symbols, footprints & 3D models
HTSSOP (PWP) 14 Ultra Librarian
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