LT3694 - 36V, 2.6A Monolithic Buck Regulator With Dual LDO

Features

  • Wide Input Range: 4V to 36V
  • Overvoltage Shutdown Protects Circuit Through 70V Transients
  • 2.6A Output Switching Regulator with Internal Power Switch
  • Dual, Low Dropout, Linear Regulator Controllers with Programmable Current Limit
  • Tracking/Soft-Start Inputs and Power Good Output Simplify Soft-Start and Supply Sequencing
  • Uses Small Inductors and Ceramic Capacitors
  • VOUT(MIN) = 0.75V (Buck and LDOs)
  • Adjustable 250kHz to 2.5MHz Switching Frequency
  • Accurate Enable Threshold Allows User Programmable Undervoltage Lockout
  • Options for Clock Synchronization (LT3694) or Clock Output to Enable Synchronization to Other Switching Regulators (LT3694-1)
  • Thermally Enhanced 28-Lead 4mm × 5mm QFN and 20-Lead TSSOP Packages
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages


Typical Application

LT3694 Typical Application
LT3694 Typical Application

Description

The LT3694/LT3694-1 are monolithic, current mode DC/DC converters with dual, low dropout regulator controllers. The switching converter is a step-down converter capable of generating up to 2.6A at its output. Each regulator has independent track/soft-start circuits simplifying power supply sequencing and interfacing with microcontrollers and DSPs.

The switching frequency is set with a single resistor with a range of 250kHz to 2.5MHz. The high switching frequency permits the use of small inductors and ceramic capacitors leading to very small triple output solutions. The constant switching frequency, combined with low impedance ceramic capacitors, results in low, predictable output ripple. Protection circuitry senses the current in the power switch and external Schottky catch diode to protect the LT3694 against short-circuit conditions. Frequency foldback and thermal shutdown provide additional protection.

With its wide input voltage range of 4V to 36V, the LT3694 regulates a broad array of power sources from 4-cell batteries and 5V logic rails to unregulated wall transformers, lead acid batteries and distributed power supplies. The LT3694 can be synchronized to an external clock with the SYNC pin while the LT3694-1 offers a CLKOUT pin allowing other DC/DC converters to synchronize to the LT3694-1 clock.

Packaging

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
Drawing
RoHS
LT3694EFE-1#PBF TSSOP-20 FE E 05-08-1663 (CB) Yes
LT3694EFE-1#TRPBF TSSOP-20 FE E 05-08-1663 (CB) Yes
LT3694EFE#PBF TSSOP-20 FE E 05-08-1663 (CB) Yes
LT3694EFE#TRPBF TSSOP-20 FE E 05-08-1663 (CB) Yes
LT3694EUFD-1#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LT3694EUFD-1#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LT3694EUFD#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LT3694EUFD#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LT3694IFE-1#PBF TSSOP-20 FE I 05-08-1663 (CB) Yes
LT3694IFE-1#TRPBF TSSOP-20 FE I 05-08-1663 (CB) Yes
LT3694IFE#PBF TSSOP-20 FE I 05-08-1663 (CB) Yes
LT3694IFE#TRPBF TSSOP-20 FE I 05-08-1663 (CB) Yes
LT3694IUFD-1#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LT3694IUFD-1#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LT3694IUFD#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LT3694IUFD#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes


LT3694 Package Drawing
LT3694 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
LT3694EFE-1#PBF TSSOP-20 E $5.71 $4.00 Yes
LT3694EFE-1#TRPBF TSSOP-20 E $4.06 Yes
LT3694EFE#PBF TSSOP-20 E $5.71 $4.00 Yes
LT3694EFE#TRPBF TSSOP-20 E $4.06 Yes
LT3694EUFD-1#PBF 4x5 QFN-28 E $5.50 $3.85 Yes
LT3694EUFD-1#TRPBF 4x5 QFN-28 E $3.91 Yes
LT3694EUFD#PBF 4x5 QFN-28 E $5.50 $3.85 Yes
LT3694EUFD#TRPBF 4x5 QFN-28 E $3.91 Yes
LT3694IFE-1#PBF TSSOP-20 I $6.29 $4.40 Yes
LT3694IFE-1#TRPBF TSSOP-20 I $4.46 Yes
LT3694IFE#PBF TSSOP-20 I $6.29 $4.40 Yes
LT3694IFE#TRPBF TSSOP-20 I $4.46 Yes
LT3694IUFD-1#PBF 4x5 QFN-28 I $6.06 $4.24 Yes
LT3694IUFD-1#TRPBF 4x5 QFN-28 I $4.30 Yes
LT3694IUFD#PBF 4x5 QFN-28 I $6.06 $4.24 Yes
LT3694IUFD#TRPBF 4x5 QFN-28 I $4.30 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
DC1541A-A LT3694EFE Demo Board | Triple Output, 4.5V ≤ VIN ≤ 36V (70V Transients), VOUT1 = 3.3V@1.7A (Buck), VOUT2 = 2.5V@450mA (LDO), VOUT3=1.8V@450mA(LDO) $125.00
Buy Now
Click here to view our complete list of demo boards

Designed for Automotive and Transportation Applications

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
LT3694IFE-1#PBF TSSOP-20 I $6.29 $4.40 Yes
LT3694IFE-1#TRPBF TSSOP-20 I $4.46 Yes
LT3694IFE#PBF TSSOP-20 I $6.29 $4.40 Yes
LT3694IFE#TRPBF TSSOP-20 I $4.46 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
  • Industrial
  • DSL and Cable Modems
  • Distributed Power Regulation
  • Wall Transformer Regulation

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Design Tools

LTspice

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

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

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

Models for the following parts are available in LTspice:
LT3694
LT3694-1

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:
LT3694

Technical Support