LTC3121 - 15V, 1.5A Synchronous Step-Up DC/DC Converter with Output Disconnect

Features

  • VIN Range: 1.8V to 5.5V, 500mV After Start-Up
  • Output Voltage Range: 2.2V to 15V
  • 400mA Output Current for VIN = 5V and VOUT = 12V
  • Output Disconnects from Input When Shut Down
  • Synchronous Rectification: Up to 95% Efficiency
  • Inrush Current Limit
  • Up to 3MHz Adjustable Switching Frequency Synchronizable to External Clock
  • Selectable Burst Mode® Operation: 25μA IQ
  • Output Overvoltage Protection
  • Soft-Start
  • <1μA IQ in Shutdown
  • 12-Lead, 3mm × 4mm Thermally Enhanced DFN Package

Typical Application

LTC3121 Typical Application
LTC3121 Typical Application

Description

The LTC®3121 is a synchronous step-up DC/DC converter with true output disconnect and inrush current limiting. The 1.5A current limit along with the ability to program output voltages up to 15V makes the LTC3121 well suited for a variety of demanding applications. Once started, operation will continue with inputs down to 500mV, extending run time in many applications.

The LTC3121 features output disconnect in shutdown, dramatically reducing input power drain and enabling VOUT to completely discharge. Adjustable PWM switching from 100kHz to 3MHz optimizes applications for highest efficiency or smallest solution footprint. The oscillator can also be synchronized to an external clock for noise sensitive applications. Selectable Burst Mode operation reduces quiescent current to 25μA, ensuring high efficiency across the entire load range. An internal soft-start limits inrush current during start-up.

Other features include a <1μA shutdown current and robust protection under short-circuit, thermal overload, and output overvoltage conditions. The LTC3121 is offered in a low profile 12-lead (3mm × 4mm × 0.75mm) DFN package.

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
LTC3121EDE#PBF 4x3 DFN-12 DE/UE E 05-08-1695 Yes
LTC3121EDE#TRPBF 4x3 DFN-12 DE/UE E 05-08-1695 Yes
LTC3121IDE#PBF 4x3 DFN-12 DE/UE I 05-08-1695 Yes
LTC3121IDE#TRPBF 4x3 DFN-12 DE/UE I 05-08-1695 Yes


LTC3121 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
LTC3121EDE#PBF 4x3 DFN-12 E $3.33 $2.33 Yes
LTC3121EDE#TRPBF 4x3 DFN-12 E $2.39 Yes
LTC3121IDE#PBF 4x3 DFN-12 I $3.90 $2.73 Yes
LTC3121IDE#TRPBF 4x3 DFN-12 I $2.79 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
DC2372A LTC3121EDE Demo Board | Sync Boost, 1.8V ≤ VIN ≤ 5.5V, Vout = 12V @ Up to 400mA $125.00
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Click here to view our complete list of demo boards

Applications

  • PCI Express Cards/Systems
  • Piezo Actuators
  • Small DC Motors
  • 12V Analog Rail From Battery, 5V, or Backup Capacitor

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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:

  • Step 1: If you have not installed LTspice on this computer, download and install LTspice
  • Step 2: Once LTspice is installed, click on the link(s) below to launch the simulation
  • Step 3: If LTspice 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:
LTC3121

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

To open the project file for this circuit:

Design tools for the following parts are available in LTpowerCAD:
LTC3121

Technical Support