Features and Benefits
- 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 × 3mm) DFN Package
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.
- 2 AA-Cell Applications
- Cellular Phones
- Digital Cameras
- MP3 Players
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
Demonstration circuit 992 is a Step-Down Converter, using the LTC3549 monolithic synchronous buck regulator. The DC992A has an input voltage range of 1.6V to 5.5V, and is capable of delivering up to 250 mA of output current at a minimum input voltage of 1.8V. The output voltage of the DC992A can be set as low as 0.611V, the reference voltage of the LTC3549. At low load currents, the DC992A can operate in either noise sensitive applications, due to the capability of the LTC3549 to operate in pulse-skipping mode, or in high efficiency applications, because the LTC3549 can also operate in Burst-Mode.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, 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.
Models for the following parts are available in LTspice:
LTpowerCAD® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.
To open the project file for this circuit:
Step 1: Download and install LTpowerCAD on your computer.
Step 2: Click on the link(s) in the section below to download part-specific project files.
Step 3: If the project file doesn't run, right-click the link and select "Save Target As." Then start the LTpowerCAD tool and open the project file by selecing "Open Project" from the "File" menu.
LTpowerCAD Project Files
Design tools for the following parts are available in LTpowerCAD:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
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 Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.