3-65V Wide Vin, Current Mode Synchronous Boost with Disconnection Switch Control


Product details


Vin (Min) (V) 3 Vin (Max) (V) 65 Vout (Min) (V) 3 Vout (Max) (V) 100 Regulated outputs (#) 1 Switching frequency (Min) (kHz) 50 Switching frequency (Max) (kHz) 1000 Iq (Typ) (mA) 4 Features Adjustable Current Limit, Enable, Frequency Synchronization, Light Load Efficiency, Synchronous Rectification, UVLO Adjustable Duty cycle (Max) (%) 100 Rating Catalog Operating temperature range (C) -40 to 125 open-in-new Find other Boost controllers (external switch)

Package | Pins | Size

HTSSOP (PWP) 20 42 mm² 6.5 x 6.4 open-in-new Find other Boost controllers (external switch)


  • 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 C6
  • Maximum Input Voltage: 65 V
  • Min Input Voltage: 3.0 V (4.5 V for startup)
  • Output Voltage Up to 100 V
  • Bypass (VOUT = VIN) Operation
  • 1.2-V Reference with ±1.0% Accuracy
  • Free-Run/Synchronizable up to 1 MHz
  • Peak Current Mode Control
  • Robust Integrated 3-A Gate Drivers
  • Adaptive Dead-Time Control
  • Optional Diode Emulation Mode
  • Programmable Cycle-by-Cycle Current Limit
  • Programmable Line UVLO
  • Programmable Soft-Start
  • Thermal Shutdown Protection
  • Low Shutdown Quiescent Current: 9 µA
  • Programmable Slope Compensation
  • Programmable Skip Cycle Mode Reduces
    Standby Power
  • Supports External VCC Bias Supply Option
  • Load Disconnection in Shutdown Mode (True
  • Inrush Current Limiting
  • Hiccup Mode Short Circuit/Overload Protection
  • Circuit Breaker Function
  • Capable of Input Transient Suppression
  • Capable of Reverse Battery Protection
  • Thermally Enhanced 20-Pin HTSSOP
open-in-new Find other Boost controllers (external switch)


The LM5121 is a synchronous boost controller intended for high-efficiency, high-power boost regulator applications. The control method is based upon peak current mode control. Current mode control provides inherent line feed-forward, cycle-by-cycle current limiting and ease of loop compensation.

The switching frequency is programmable up to 1 MHz. Higher efficiency is achieved using two robust N-channel MOSFET gate drivers with adaptive dead-time control. A user-selectable diode emulation mode enables discontinuous mode operation for improved efficiency at light load conditions.

The LM5121 provides disconnection switch control which completely disconnects the output from the input during an output short or a shutdown condition. During start-up sequence, inrush current is limited by the disconnection switch control.

An internal charge pump allows 100% duty cycle operation of the high-side synchronous switch (Bypass operation). Additional features include thermal shutdown, frequency synchronization, hiccup mode current limit and adjustable line undervoltage lockout.

open-in-new Find other Boost controllers (external switch)

Technical documentation

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Type Title Date
* Datasheet LM5121/-Q1 Wide Input Synchronous Boost Controller with Disconnection Switch Control datasheet (Rev. C) Jun. 14, 2016
Technical articles How to add overvoltage protection to a synchronous boost controller Sep. 17, 2018
Application notes Designing the front-end DC/DC conversion stage to withstand automotive transient Jan. 18, 2017
Application notes Designing Fault Protection Circuits Using Wide VIN LM5121 Jan. 12, 2015
Technical articles Exploiting current-mode control for wide Vin DC/DC conversion Aug. 14, 2014
White papers How to design boost, SEPIC or flyback regulators with wide VIN power ICs Jul. 29, 2014
Application notes Practical Feedback Loop Analysis for Current-Mode Boost Converter Mar. 07, 2014
Application notes Automated Frequency Response Analyzer Oct. 09, 2013
User guides LM5121EVM Evaluation Module Aug. 23, 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 LM5121EVM evaluation module (EVM) provides the design engineer with a fully functional synchronous boost converter to evaluate the Texas Instruments LM5121 synchronous boost controller IC including disconnection switch control. The EVM provides 12V output at up to 2A current from a 3.0V (5.7V (...)
  • 3V to 12V input range (5.7V for start-up)
  • 12V/2A output
  • 250kHz switching frequency
  • Programmable light load operation
  • Inrush current limit, short circuit protection

Design tools & simulation

SNVM505A.ZIP (115 KB) - PSpice Model
SNVM962.ZIP (7 KB) - PSpice Model
SNVMA47A.ZIP (53 KB) - TINA-TI Spice Model
SNVMA48.TSC (192 KB) - TINA-TI Reference Design
PSpice® for TI design and simulation tool
PSPICE-FOR-TI — PSpice® for TI is a design and simulation environment that helps evaluate functionality of analog circuits. This full-featured, design and simulation suite uses an analog analysis engine from Cadence®. Available at no cost, PSpice for TI includes one of the largest model libraries in the (...)
  • Leverages Cadence PSpice Technology
  • Preinstalled library with a suite of digital models to enable worst-case timing analysis
  • Dynamic updates ensure you have access to most current device models
  • Optimized for simulation speed without loss of accuracy
  • Supports simultaneous analysis of multiple products
  • (...)

Reference designs

High Density 72W Battery Powered Synchronous Boost Reference Design
PMP11422 PMP11422 is a synchronous boost power supply using the LM5121 controllers. The design accepts an input voltage of 5Vin to 8.6Vin, and boosts a 12Vout rail capable of sourcing 6A continuous current. The LM5121 integrates an input disconnection switch feature which allows boost short circuit (...)
document-generic Schematic document-generic User guide
8V @ 7A Synchronous Boost Reference Design with LM5121
PMP10092 The PMP10092 reference design is a synchronous boost converter that can operate over a 3V to 8V input range and produce an 8V output at 7A load. The circuit has an output disconnection switch for safety. Due to the synchronous design a high efficiency of 97% can be achieved.
document-generic Schematic document-generic User guide
150W Boost Converter with LM5121 Reference Design
PMP8673 The PMP8673 reference design is a synchronous boost converter optimized for high efficiency while maintaining a small form factor. This reference design has a voltage input range of 34.5-37.5V (35V nominal) and provides an output voltage of 55.5V. The synchronous boost topology enables efficiencies (...)
document-generic Schematic document-generic User guide
Single Phase 60W Audio Amplifier Reference Design
PMP9372 PMP9372 is a single-phase synchronous boost converter, which utilizes the LM5121 controller. Inrush limiting is set to 11A nominal, which allows startup into a 4700μF output capacitor. The TPS3700DDC is used as an output voltage monitor, which provides Power Good signaling of output over-voltage (...)
document-generic Schematic document-generic User guide
document-generic Schematic document-generic User guide

CAD/CAE symbols

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HTSSOP (PWP) 20 View options

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