LTC3549 - 250mA Low VIN Buck Regulator in 2mm x 3mm DFN

Features

  • 1.6V to 5.5V Input Voltage Range
  • Internal Soft-Start
  • Low Ripple Burst Mode® Operation
      Output Ripple: <20mVP-P
      IQ: 50µA
  • 2.25MHz Constant-Frequency Operation
  • High Effi ciency: Up to 93%
  • 250mA Output Current (VIN = 1.8V, VOUT = 1.2V)
  • 450mA Peak Inductor Current
  • No Schottky Diode Required
  • Low Dropout Operation: 100% Duty Cycle
  • 0.611V Reference Voltage
  • Stable with Ceramic Capacitors
  • Shutdown Mode Draws <1µA Supply Current
  • Current Mode Operation for Excellent Line and Load Transient Response
  • Overtemperature Protection
  • Available in a Low Profi le (0.75mm) 6-Lead (2mm x 3mm) DFN Package

Typical Application

LTC3549 Typical Application
LTC3549 Typical Application

Description

The LTC3549 is a high efficiency, monolithic synchronous buck regulator using a constant-frequency, current mode architecture. The output voltage is adjusted via an external resistor divider.

 A fixed switching frequency of 2.25MHz is supported. This switching frequency allows the use of small surface mount inductors and capacitors, including ceramics.

 Supply current during Burst Mode operation is only 50µA dropping to < 1µA in shutdown. The 1.6V to 5.5V input voltage range makes the LTC3549 ideally suited for single cell Li-Ion, Li-Metal and 2-cell alkaline, NiCd or NiMH battery-powered applications. 100% duty cycle capability provides low dropout operation, extending battery life in portable systems. Burst Mode operation can be user-enabled, increasing efficiency at light loads, further extending battery life.

 The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. Internal soft-start offers controlled output voltage rise time at startup without the need for external components.

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
LTC3549EDCB#PBF 2x3 DFN-6 DCB E 05-08-1715 Yes
LTC3549EDCB#TRMPBF 2x3 DFN-6 DCB E 05-08-1715 Yes
LTC3549EDCB#TRPBF 2x3 DFN-6 DCB E 05-08-1715 Yes


LTC3549 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
LTC3549EDCB#PBF 2x3 DFN-6 E $2.06 Yes
LTC3549EDCB#TRMPBF 2x3 DFN-6 E $2.06 $1.49 Yes
LTC3549EDCB#TRPBF 2x3 DFN-6 E $2.06 $1.44 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
DC992A LTC3549EDCB Demo Board $75.00
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Click here to view our complete list of demo boards

Applications

  • 2 AA-Cell Applications
  • Cellular Phones
  • Digital Cameras
  • MP3 Players

Product Notifications

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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:
LTC3549

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:

  • Step 1: If you have not installed LTpowerCAD on this computer, download and install LTpowerCAD
  • Step 2: Once LTpowerCAD is installed, click on the link(s) below to open the project file
  • Step 3: If LTpowerCAD does not automatically open after clicking the link above, you can open the project file by right clicking on the link and selecting "Save Target As." After saving the file to your computer, start LTpowerCAD and open the project file by selecting 'Open Project' from the 'File' menu

Design tools for the following parts are available in LTpowerCAD:
LTC3549

Technical Support