4.5-36V, 3A Current Mode Synchronous Buck Regulator with Frequency Synchronization


Product details


Vin (Min) (V) 4.5 Vin (Max) (V) 36 Vout (Min) (V) 0.8 Vout (Max) (V) 32 Iout (Max) (A) 3 Iq (Typ) (uA) 2300 Switching frequency (Min) (kHz) 250 Switching frequency (Max) (kHz) 1500 Features Enable, Frequency Synchronization, Over Current Protection, Power Good, Pre-Bias Start-Up, Synchronous Rectification, Tracking Operating temperature range (C) -40 to 125 Rating Catalog Regulated outputs (#) 1 open-in-new Find other Buck converters (integrated switch)

Package | Pins | Size

HTSSOP (PWP) 20 42 mm² 6.5 x 6.4 open-in-new Find other Buck converters (integrated switch)


  • 4.5V to 36V Input Voltage Range
  • 3A Output Current, 5.2A Peak Current
  • 130 mΩ/110 mΩ Integrated Power MOSFETs
  • 94% Peak Efficiency with Synchronous Rectification
  • 1.5% Feedback Voltage Accuracy
  • Current Mode Control, Selectable Compensation
  • Oscillator Synchronization from 250kHz to 1.5MHz
  • Adjustable Output Voltage Down to 0.8V
  • Compatible with Pre-biased Loads
  • Programmable Soft-start with External Capacitor
  • Precision Enable Pin with Hysteresis
  • OVP, UVLO Inputs and PGOOD Output
  • Internally Protected with Peak Current Limit, Thermal Shutdown and Restart
  • Accurate Current Limit Minimizes Inductor Size
  • Non-linear Current Mode Slope Compensation
  • 20-Pin HTSSOP Exposed Pad Package

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The LM20333 is a full featured synchronous buck regulator capable of delivering up to 3A of load current. The current mode control loop is externally compensated with only two components, offering both high performance and ease of use. The device is optimized to work over the input voltage range of 4.5V to 36V making it well suited for high voltage systems.

The device features internal Over Voltage Protection (OVP) and Over Current Protection (OCP) circuits for increased system reliability. A precision Enable pin and integrated UVLO allows the turn on of the device to be tightly controlled and sequenced. Startup inrush currents are limited by both an internally fixed and externally adjustable soft-start circuit. Fault detection and supply sequencing are possible with the integrated power good (PGOOD) circuit.

The LM20333 is designed to work well in multi-rail power supply architectures. The output voltage of the device can be configured to track a higher voltage rail using the SS/TRK pin. If the output of the LM20333 is pre-biased at startup it will not sink current to pull the output low until the internal soft-start ramp exceeds the voltage at the feedback pin.

The switching frequency of the LM20333 can be synchronized to an external clock by use of the SYNC pin. The SYNC pin is capable of synchronizing to input signals ranging from 250 kHz to 1.5 MHz.

The LM20333 is offered in an exposed pad 20-pin HTSSOP package that can be soldered to the PCB, eliminating the need for bulky heatsinks.

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Technical documentation

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Type Title Date
* Datasheet LM20333 36V, 3A Synchronous Buck Regulator with Frequency Synchronization datasheet (Rev. D) Apr. 03, 2013
Technical article Minimize the impact of the MLCC shortage on your power application Mar. 29, 2019
Selection guide Power Management Guide 2018 (Rev. R) Jun. 25, 2018
User guide AN-1791 LM20333 Evaluation Board (Rev. B) May 05, 2013

Design & development

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Hardware development

document-generic User guide

This evaluation board provides a solution to examine the full featured LM20333 buck switching regulator that is capable of driving up to 3A of load current. This device features a clock synchronization input that allows the switching frequency to be synchronized to an external clock source. The (...)

Design tools & simulation

SNVM369.TSC (199 KB) - TINA-TI Reference Design
SNVM370.ZIP (11 KB) - TINA-TI Spice Model
SNVM371.ZIP (8 KB) - TINA-TI Spice Model
SNVM372.TSC (72 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
  • (...)
LM20333 Calculator spreadsheet

Reference designs

Multiple Output Power Solution for Kintex 7 Application
PMP7804 The PMP7804 reference design provides all the power supply rails necessary to power the Xilinx ® Kintex ® 7 series family of FPGAs.  This design utilizes Simple Switcher power modules along with the LM2121x low voltage synchronous buck regulators for "ease of use" and shorter design (...)
document-generic Schematic document-generic User guide

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HTSSOP (PWP) 20 View options

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