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


Product details


Vin (Min) (V) 4.5 Vin (Max) (V) 100 Switching frequency (Max) (kHz) 1000 Soft start Adjustable Features Enable, Light Load Efficiency, Pre-Bias Start-Up, Synchronous Rectification Operating temperature range (C) -40 to 125 Iout (A) 1 Product type Converter (Integrated switch) Topology Buck open-in-new Find other Flybuck converters

Package | Pins | Size

HTSSOP (PWP) 14 32 mm² 5 x 6.4 open-in-new Find other Flybuck converters


  • Qualified for Automotive Applications
  • AEC-Q100 Qualified With the Following Results:
    • Device Temperature Grade 1: –40°C to 125°C Ambient Operating Temperature Range
    • Device HBM ESD Classification Level 2
    • Device CDM ESD Classification Level C5
  • 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-Q1 With the WEBENCH® Power Designer

All trademarks are the property of their respective owners.

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The LM5161-Q1 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-Q1 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-Q1 supports the multiple output and isolated Fly-Buck applications. When programmed for the DCM operation, the LM5161-Q1 provides a tightly regulated buck output without any additional external feedback ripple injection circuit.

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Technical documentation

= Top documentation for this product selected by TI
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Type Title Date
* Datasheet LM5161-Q1 Wide Input 100-V, 1-A Synchronous Buck/Fly-Buck™ Converter datasheet (Rev. A) Nov. 30, 2017
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 note Powering Drones With a Wide VIN DC-DC Converter (Rev. A) Feb. 05, 2019
Application note EMI and Thermal Design Tips and Tricks for 48-V IGBT/SiC/GaN Automotive Supply Jul. 27, 2018
Technical articles Why a wide VIN DC/DC converter is a good fit for high-cell-count battery-powered drones Nov. 21, 2017
Technical articles Simplifying 100V wide VIN power conversion Nov. 11, 2016
User guide LM5161 Fly-Buck (Isolated Buck) EVM User’s Guide (Rev. A) Aug. 19, 2016
User guide LM5161PWPBKEVM Buck Evaluation Module User's Guide (Rev. A) Aug. 19, 2016
Technical articles Create a Fly-Buck™ converter in WEBENCH® Power Designer Oct. 09, 2015
White paper Designing isolated rails on the fly with Fly-Buck™ converters Sep. 29, 2015
Technical articles How to design for EMC and isolation with Fly-Buck™ converters Jul. 28, 2015
Application note Is Your IGBT Gate-Driver Power Supply Optimized Mar. 12, 2015
Application note 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

Design & development

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

Hardware development

document-generic User guide
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 (...)
  • 15V to 80V input voltage range
  • 12V target output voltage
  • Delivers up to 1.0A output load current
  • FPWM mode pin feature to choose between CCM and DCM
document-generic User guide
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 (...)
  • 36V to 72V input voltage range
  • 12V target secondary isolated output voltage
  • Delivers up to 800mA secondary output load current

Design tools & simulation

SNVMAV3.ZIP (499 KB) - PSpice Model
SNVMAV4.ZIP (3 KB) - PSpice Model

Reference designs

-60 V inverting buck-boost reference design
PMP30603 — This tiny reference design delivers -60-V output voltage from an input voltage around 5 V typically generated by an automotive pre regulator. The controller in that circuit is LM5161-Q1 providing two internal MOSFETs. Overall, this converter is used as auxiliary supply for LIDAR applications. 
document-generic Schematic document-generic User guide
Dual-Output LM5161-Q1 Fly-Buck™ Reference Design With an Ultra-Small Coupled Inductor
PMP15007 — PMP15007 uses the LM5161-Q1 in a Fly-Buck topology with the primary and secondary output both set to 5V nominal. The circuit accommodates a voltage input range from 36V to 72V, ideal for the 48V nominal input rail. While the primary side is set at 5.32V nominally, the secondary isolated side sees 5V (...)
document-generic Schematic document-generic User guide

CAD/CAE symbols

Package Pins Download
HTSSOP (PWP) 14 View options

Ordering & quality

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