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

Features

  • 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
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages


Typical Application

LT3690 Typical Application
LT3690 Typical Application

Description

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.

Packaging

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

Part Number Package Code Temp Package
Drawing
RoHS
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
(1-99)
Price
(1k)*
RoHS
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
Buy NowRequest Samples
* 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
Buy Now
Click here to view our complete list of demo boards

Designed for Automotive and Transportation Appications

AEC-Q100 data is available for these specific part numbers. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. For more information, view our Automotive and Transportation page

Part Number Package Temp Price
(1-99)
Price
(1k)*
RoHS
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
Buy NowRequest Samples
* 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.

Applications

  • Automotive Systems
  • Industrial Supplies
  • Distributed Supply Regulation

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Design Tools

LTpowerCAD

The LTpowerCAD design tool is a complete power supply design tool program that can significantly ease the tasks of power supply design. It guides users to a solution, selects power stage components, provides detailed power efficiency, shows quick loop bode plot stability and load transient analysis, and can export a final design to LTspice for simulation. Click here to download LTpowerCAD

Design tools for the following parts are available in LTpowerCAD:
LT3690

LTspiceIV

LTspice® IV 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 IV

To launch a ready to run LTspice demonstration circuit for this part:

  • Step 1: If you have not installed LTspice on this computer, download and install LTspice IV
  • Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
  • Step 3: If LTspice IV does not automatically open after clicking the link above, 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

To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.

Models for the following parts are available in LTspice IV:
LT3690

Technical Support