Powerelectronics 1895 1004linear

Step-Down Switching Regulator Offers 100% Duty Cycle Operation

Oct. 9, 2013
Linear Technology Corporation announces the LT3514, a triple output, 36 V step-down switching regulator with 100% duty cycle operation.

The LT3514 is a triple output, 36 V step-down switching regulator from Linear Technology Corp. with 100% duty cycle operation. The LT3514 delivers 2 A of continuous output current from one channel and 1A each from the other two channels at voltages as low as 0.8 V. The device's 3.2 V to 36 V (40 V MAX) input voltage range makes it ideal for automotive and industrial applications that require multiple outputs. The LT3514's unique design includes an onboard boost regulator, enabling each channel to operate at 100% duty cycle, even with input voltage as low as 3.2 V. This architecture makes the LT3514 well suited for applications requiring continuous output regulation such as automotive cold-crank and stop-start scenarios.

The LT3514's switching frequency is user-programmable from 250 kHz to 2.2 MHz and is synchronizable throughout the range, enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency bands. The combination of its 28-lead 4mm x 5mm QFN package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint for multiple output applications.

The LT3514 utilizes one internal 3 A switch and two 1.45 A switches for the step-down conversion and a 220 mA switch for the internal boost circuit, with the necessary oscillator, control and logic circuitry integrated into a single die. Special design techniques deliver efficiencies up to 88% over a wide input voltage range, and the LT3514's current mode topology enables fast transient response and excellent loop stability. Anti-phase switching reduces input ripple and robust short-circuit protection enhances system reliability. Other features include output voltage tracking, programmable undervoltage lockout and a power good pin to indicate when all outputs are in regulation.

The LT3514 is available in thermally enhanced 4mm x 5mm QFN-28 and TSSOP-24 packages. The LT3514E is priced starting at $3.50 each for 1,000-piece quantities. The LT3514I is tested and guaranteed to operate from a -40 °C to 125 °C junction temperature range and is priced starting at $3.85 each for 1,000-piece quantities. Both versions are available from stock.


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