Product details

Vin (Max) (V) 100 Vin (Min) (V) 4.5 Iout (Max) (A) 1 Features Enable, Light Load Efficiency, Pre-Bias Start-Up, Synchronous Rectification Operating temperature range (C) -40 to 125 Regulated outputs (#) 1 Package type HTSSOP(14)
Vin (Max) (V) 100 Vin (Min) (V) 4.5 Iout (Max) (A) 1 Features Enable, Light Load Efficiency, Pre-Bias Start-Up, Synchronous Rectification Operating temperature range (C) -40 to 125 Regulated outputs (#) 1 Package type HTSSOP(14)
HTSSOP (PWP) 14 32 mm² 5 x 6.4
  • 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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Type Title Date
* Data sheet LM5161 Wide Input 100-V, 1-A Synchronous Buck/Fly-Buck™ Converter datasheet (Rev. B) 27 Nov 2017
Application note Step-Dwn (Buck) Convrtr Pwer Solutions for Programmable Logic Controller Systems (Rev. A) 26 Jul 2021
Selection guide Buck Converter Quick Reference Guide (Rev. B) 08 Apr 2021
White paper Valuing wide VIN, low EMI synchronous buck circuits for cost-driven, demanding a (Rev. A) 10 Apr 2019
Application note Stability Analysis and Design of COT Type-3 Ripple Circuit 20 Mar 2019
Application note Powering Drones With a Wide VIN DC-DC Converter (Rev. A) 05 Feb 2019
Technical article Why a wide VIN DC/DC converter is a good fit for high-cell-count battery-powered drones 21 Nov 2017
Technical article Simplifying 100V wide VIN power conversion 11 Nov 2016
User guide LM5161 Fly-Buck (Isolated Buck) EVM User’s Guide (Rev. A) 19 Aug 2016
User guide LM5161PWPBKEVM Buck Evaluation Module User's Guide (Rev. A) 19 Aug 2016
Technical article Create a Fly-Buck™ converter in WEBENCH® Power Designer 09 Oct 2015
White paper Designing isolated rails on the fly with Fly-Buck™ converters 29 Sep 2015
Technical article How to design for EMC and isolation with Fly-Buck™ converters 28 Jul 2015
Application note Is Your IGBT Gate-Driver Power Supply Optimized 12 Mar 2015
Application note Fly-Buck(TM) converter provides EMC and isolation in PLC applications 29 Jan 2015
Application note AN-2292 Designing an Isolated Buck (Fly-Buck) Converter (Rev. C) 17 Dec 2014
White paper Wide VIN power management ICs simplify white paper (Rev. A) 19 Sep 2013
Application note AN-2218 Precision Current Limiting with the LMP8646 and LM3102 (Rev. A) 23 Apr 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 (...)
In stock
Limit: 5
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 (...)
In stock
Limit: 5
Simulation model

LM5161 PSpice Buck and Fly-Buck Transient Model

SNVMAV3.ZIP (499 KB) - PSpice Model
Simulation model

LM5161 Unencrypted PSpice Buck and Fly-Buck Transient Model

SNVMAV4.ZIP (3 KB) - PSpice Model
Calculation tool

FLYBUCK-FLYBACK-DESIGN-CALC — Fly-Buck and Flyback Topology Selector

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.
Calculation tool

LM5161 Buck Quick Start Component Selector

SNVC199.ZIP (383 KB)
Calculation tool

LM5161 Fly-Buck Quick Start Component Selector

SNVC200.ZIP (287 KB)
Reference designs

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 (...)
Reference designs

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 (...)
Reference designs

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 & (...)
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