Alternative Parts

  • LT8614
    LT8614

    42V, 4A Synchronous Step-Down Silent Switcher with 2.5μA Quiescent Current

  • LT8640S
    LT8640S

    42V, 6A Synchronous Step-Down Silent Switcher 2 with 2.5μA Quiescent Current

  • LT8641
    LT8641

    65V, 3.5A Synchronous Step-Down Silent Switcher with 2.5μA Quiescent Current

Overview

Features and Benefits

  • Silent Switcher® Architecture
    • Ultralow EMI/EMC Emissions
    • Spread Spectrum Frequency Modulation
  • High Efficiency at High Frequency
    • Up to 96% Efficiency at 1MHz, 12VIN to 5VOUT
    • Up to 95% Efficiency at 2MHz, 12VIN to 5VOUT
  • Wide Input Voltage Range: 3.4V to 42V
  • 5A Maximum Continuous Output, 7A Peak Transient Output
  • Ultralow Quiescent Current Burst Mode® Operation
    • 2.5μA IQ Regulating 12VIN to 3.3VOUT
    • Output Ripple < 10mVP-P
  • Fast Minimum Switch-On Time: 30ns
  • Low Dropout Under All Conditions: 100mV at 1A
  • Forced Continuous Mode (LT8640-1 Only)
  • Safely Tolerates Inductor Saturation in Overload
  • Adjustable and Synchronizable: 200kHz to 3MHz
  • Peak Current Mode Operation
  • Output Soft-Start and Tracking
  • Small 18-Lead 3mm × 4mm QFN

Product Details

The LT8640/LT8640-1 step-down regulator features Silent Switcher architecture designed to minimize EMI/EMC emissions while delivering high efficiency at frequencies up to 3MHz. Assembled in a 3mm × 4mm QFN, the monolithic construction with integrated power switches and inclusion of all necessary circuitry yields a solution with a minimal PCB footprint. An ultralow 2.5μA quiescent current—with the output in full regulation—enables applications requiring highest efficiency at very small load currents. Transient response remains excellent and output voltage ripple is below 10mVP-P at any load, from zero to full current.

The LT8640/LT8640-1 allows high VIN to low VOUT conversion at high frequency with a fast minimum top switch on-time of 35ns. Operation is safe in overload even with a saturated inductor.

Essential features are included and easy to use: An open-drain PG pin signals when the output is in regulation. The SYNC/MODE pin selects between Burst Mode operation, spread spectrum mode, synchronization to an external clock, and either pulse-skipping (LT8640) or forced continuous mode (LT8640-1). Soft-start and tracking functionality is accessed via the TR/SS pin. An accurate enable threshold can be set using the EN/UV pin and a resistor at the RT pin programs switch frequency.

Applications

  • Automotive and Industrial Supplies
  • General Purpose Step-Down
  • GSM Power Supplies

Product Lifecycle icon-recommended Production

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.

Evaluation Kits (1)

Tools & Simulations

LTspice

LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.

To launch ready-to-run LTspice demonstration circuits for this part:

Step 1: Download and install LTspice on your computer.

Step 2: Click on the link in the section below to download a demonstration circuit.

Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.

LTspice

Models for the following parts are available in LTspice:

LT8640
LT8640-1

LTpowerCAD

LTpowerCAD® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.

To open the project file for this circuit:

Step 1: Download and install LTpowerCAD on your computer.

Step 2: Click on the link(s) in the section below to download part-specific project files.

Step 3: If the project file doesn't run, right-click the link and select "Save Target As." Then start the LTpowerCAD tool and open the project file by selecing "Open Project" from the "File" menu.

LTPowerCAD

Design tools for the following parts are available in LTpowerCAD:

LT8640

Product Recommendations

LT8640 Companion Parts

Recommended Related Parts

Design Resources

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well.  "Zero defects" for shipped products is always our goal.

Sample & Buy

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The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


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Evaluation Boards Pricing displayed is based on 1-piece.
Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.