LT3690 - 36V, 4A, 1.5MHz Synchronous Step-Down Switching Regulator with 70μA Quiescent Current


  • Wide Input Range:
    – Operation from 3.9V to 36V
    – Overvoltage Lockout Protects Circuits Through 60V Transients
  • 4A Maximum Output Current
  • Integrated 30mΩ N-Channel Synchronous Switch
  • Low Ripple (<15mVP-P) Burst Mode® Operation:
    IQ = 70μA at 12VIN to 3.3VOUT
  • Programmable Input Undervoltage Lockout
  • 0.8V Feedback Reference Voltage
  • Output Voltage: 0.8V to 20V
  • Programmable and Synchronizable Oscillator
    (170kHz to 1.5MHz)
  • Soft-Startup and Output Voltage Tracking
  • Short-Circuit Robust
  • Power Good Flag
  • Small Thermally Enhanced 4mm × 6mm QFN Package

Typical Application

LT3690 Typical Application
LT3690 Typical Application


The LT3690 is an adjustable frequency monolithic buck switching regulator that accepts input voltages up to 36V. A high efficiency 90mΩ switch is included on the device along with the boost diode and the necessary oscillator, control, and logic circuitry. The internal synchronous power switch of 30mΩ increases efficiency and eliminates the need for an external Schottky catch diode. Current mode topology is used for fast transient response and good loop stability. Shutdown reduces input supply current to less than 1μA. The low ripple Burst Mode maintains high efficiency at low output currents while keeping output ripple below 15mV in typical applications.

The LT3690 features robust operation and is easily configurable. Using a resistor divider on the UVLO pin provides a programmable undervoltage lockout. A power good flag signals when VOUT reaches 90% of the programmed output voltage. Protection circuitry senses the current in the power switches to protect the LT3690 against short-circuit conditions. Frequency foldback and thermal shutdown provide additional protection. The LT3690 is available in a 4mm × 6mm QFN package with exposed pads for low thermal resistance.


CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
LT3690EUFE#PBF 4x6 QFN-26 UFEMA E 05-08-1770 Yes
LT3690EUFE#TRPBF 4x6 QFN-26 UFEMA E 05-08-1770 Yes
LT3690HUFE#PBF 4x6 QFN-26 UFEMA H 05-08-1770 Yes
LT3690HUFE#TRPBF 4x6 QFN-26 UFEMA H 05-08-1770 Yes
LT3690IUFE#PBF 4x6 QFN-26 UFEMA I 05-08-1770 Yes
LT3690IUFE#TRPBF 4x6 QFN-26 UFEMA I 05-08-1770 Yes
LT3690MPUFE#PBF 4x6 QFN-26 UFEMA MP 05-08-1770 Yes
LT3690MPUFE#TRPBF 4x6 QFN-26 UFEMA MP 05-08-1770 Yes

LT3690 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
LT3690EUFE#PBF 4x6 QFN-26 E $7.07 $4.95 Yes
LT3690EUFE#TRPBF 4x6 QFN-26 E $5.01 Yes
LT3690HUFE#PBF 4x6 QFN-26 H $8.14 $5.70 Yes
LT3690HUFE#TRPBF 4x6 QFN-26 H $5.76 Yes
LT3690IUFE#PBF 4x6 QFN-26 I $7.79 $5.45 Yes
LT3690IUFE#TRPBF 4x6 QFN-26 I $5.51 Yes
LT3690MPUFE#PBF 4x6 QFN-26 MP $21.00 $14.70 Yes
LT3690MPUFE#TRPBF 4x6 QFN-26 MP $14.76 Yes
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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 Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC1520A LT3690EUFE Demo Board | 4.5V ≤ VIN ≤ 36V, VOUT = 3.3V @ 4A, Fsw=450kHz $150.00
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Click here to view our complete list of demo boards


  • Automotive Systems
  • Industrial Supplies
  • Distributed Supply Regulation

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Design Tools


LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice

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