Features and Benefits
- Single Inductor
- Fixed Frequency Operation with Battery Voltages
- Above, Below or Equal to the Output
- Synchronous Rectification: Up to 96% Efficiency
- 25µA Quiescent Current in Burst Mode® Operation
- Up to 600mA Continuous Output Current
- No Schottky Diodes Required (VOUT < 4.3V)
- VOUT Disconnected from VIN During Shutdown
- 2.5V to 5.5V Input and Output Range
- Programmable Oscillator Frequency from 300kHz to 2MHz
- Synchronizable Oscillator
- Burst Mode Enable Control
- <1µA Shutdown Current
- Small Thermally Enhanced 10-Pin MSOP and (3mm × 3mm) DFN Packages
The LTC3440 is a high efficiency, fixed frequency, Buck-Boost DC/DC converter that operates from input voltages above, below or equal to the output voltage. The topology incorporated in the IC provides a continuous transfer function through all operating modes, making the product ideal for single lithium-ion, multicell alkaline or NiMH applications where the output voltage is within the battery voltage range.
The device includes two 0.19Ω N-channel MOSFET switches and two 0.22Ω P-channel switches. Switching frequencies up to 2MHz are programmed with an external resistor and the oscillator can be synchronized to an external clock. Quiescent current is only 25µA in Burst Mode operation, maximizing battery life in portable applications. Burst Mode operation is user controlled and can be enabled by driving the MODE/SYNC pin high. If the MODE/SYNC pin has either a clock or is driven low, then fixed frequency switching is enabled.
Other features include a 1µA shutdown, soft-start control, thermal shutdown and current limit. The LTC3440 is available in the 10-pin thermally enhanced MSOP package.
Protected by U.S. Patents including 6404251, 6166527.
- Palmtop Computers
- Handheld Instruments
- MP3 Players
- Digital Cameras
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 (2)
Demonstration Circuit 797 is a constant-frequency synchronous Buck-Boost converter using the LTC3440EDD in the 3mm × 3mm DFN-10 package. The input range is from 2.5V to 5.5V, making it ideal for single-cell Lithium-Ion or three-cell NiCd/NiMH battery applications. For 2.7V minimum input voltage, this converter can provide up to 600mA load current. The output voltage is set at 3.3V. A different output voltage in the range of 2.5V to 5.25V can be obtained by changing one of the feedback resistors.
Demonstration Circuit 425B is a constant-frequency synchronous Buck-Boost converter using the LTC3440. The input range is from 2.5V to 5.5V, making it ideal for single-cell lithium-ion or three-cell NiCd/NiMH battery applications. For 2.7V minimum input voltage, this converter can provide up to 600mA load current. The output voltage is set at 3.3V. A different output voltage in the range of 2.5V to 5.5V can be obtained by changing one of the feedback resistors.
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:
Technical Articles (4)
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.
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