1. Products
  2. Power Management
  3. Switching Regulators
  4. Step-Down (Buck) Regulators
  5. External Power Switch Buck Controllers
  6. LTC3809-1


Features and Benefits

  • Programmable Output Voltage Tracking
  • No Current Sense Resistor Required
  • Constant Frequency Current Mode Operation for Excellent Line and Load Transient Response
  • Wide VIN Range: 2.75V to 9.8V
  • Wide VOUT Range: 0.6V to VIN
  • 0.6V ±1.5% Reference
  • Low Dropout Operation: 100% Duty Cycle
  • Selectable Burst Mode®/Pulse-Skipping/Forced Continuous Operation
  • Auxiliary Winding Regulation
  • Internal Soft-Start Circuitry
  • Selectable Maximum Peak Current Sense Threshold
  • Output Overvoltage Protection
  • Micropower Shutdown: IQ = 9µA
  • Tiny Thermally Enhanced Leadless (3mm × 3mm) DFN or 10-lead MSOP Packages

Product Details

The LTC3809-1 is a synchronous step-down switching regulator controller that drives external complementary power MOSFETs using few external components. The constant frequency current mode architecture with MOSFET VDS sensing eliminates the need for a current sense resistor and improves efficiency.

Optional Burst Mode operation provides high efficiency operation at light loads. 100% duty cycle provides low dropout operation, extending operating time in battery-powered systems. Burst Mode is inhibited when the MODE pin is pulled low to reduce noise and RF interference.

The LTC3809-1 allows either coincident or ratiometric output voltage tracking. Switching frequency is fixed at 550kHz. Fault protection is provided by an overvoltage comparator and a short-circuit current limit comparator.

The LTC3809-1 is available in tiny footprint thermally enhanced DFN and 10-lead MSOP packages.

Features Package
LTC3809 PLL, Selectable Spread Spectrum, Power Good 3x3 DFN-10, MS-10E
LTC3809-1 Tracking 3x3 DFN-10, MS-10E
LTC3808 PLL, Selectable Spread Spectrum, Tracking, Power Good 4x3 DFN-14, SSOP-16


  • 1- or 2-Cell Lithium-Ion Powered Devices
  • Notebook and Palmtop Computers, PDAs
  • Portable Instruments
  • Distributed DC Power Systems

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® 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.


Models for the following parts are available in LTspice:


Product Recommendations

LTC3809-1 Companion Parts

Recommended Related Parts

Recommended Suggested Oscillator

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.View our quality and reliability program and certifications for more information.

Part Number Material Declaration Reliability Data Pin/Package Drawing CAD Symbols, Footprints & 3D Models
LTC3809EDD-1#PBF Material Declaration Reliability Data 10-Lead DFN (3mm x 3mm w/ EP)
LTC3809EDD-1#TRPBF Material Declaration Reliability Data 10-Lead DFN (3mm x 3mm w/ EP)
LTC3809EMSE-1#PBF Material Declaration Reliability Data 10-Lead MSOP w/ EP
LTC3809EMSE-1#TRPBF Material Declaration Reliability Data 10-Lead MSOP w/ EP
LTC3809IDD-1#PBF Material Declaration Reliability Data 10-Lead DFN (3mm x 3mm w/ EP)
LTC3809IDD-1#TRPBF Material Declaration Reliability Data 10-Lead DFN (3mm x 3mm w/ EP)
LTC3809IMSE-1#PBF Material Declaration Reliability Data 10-Lead MSOP w/ EP
LTC3809IMSE-1#TRPBF Material Declaration Reliability Data 10-Lead MSOP w/ EP
Wafer Fabrication Data R421 Reliability Data

PCN-PDN Information

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Sample & Buy

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Lead Times

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Evaluation Boards

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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.