Synchronous buck-boost controller eliminates surge protection

Analog Devices, Inc., which recently acquired Linear Technology Corporation, has announced the LTC3779, a high efficiency (up to 99%) 4-switch single inductor synchronous buck-boost DC/DC controller that operates from input voltages above, below or equal to the regulated output voltage. Its 4.5V to 150V input voltage range is designed to operate from a high input voltage source or from an input that has high voltage surges, eliminating the need for external surge suppression devices, ideal for transportation, industrial and military applications.

The output voltage can be set from 1.2V to 150V at output currents up to 10s of amps, depending on the choice of external components. The LTC3779’s powerful 1.3Ω N-channel MOSFET gate drivers can be adjusted from 6V to 10V, enabling the use of logic-level or standard threshold MOSFETs. To prevent high on-chip power dissipation in high input voltage applications, the LTC3779 includes an NDRV pin which drives the gate of an optional external N-channel MOSFET acting as a low dropout linear regulator to supply IC bias power. The EXTVcc pin permits the LTC3779 to be powered from the output or other available source up to 36V, reducing power dissipation and improving efficiency.

Output power up to 500W can be delivered with a single device. Higher power can be achieved when multiple circuits are configured in parallel. The operating frequency is selectable between 50kHz and 600kHz, and can be synchronised to an external clock over the same range. The LTC3779 employs a proprietary current mode control architecture for constant-frequency operation in buck or boost mode. The user can select either forced continuous mode or discontinuous mode to maximise light load efficiency.

Additional features include input or output average current limit, a power good output voltage monitor, adjustable soft-start and input overvoltage lockout and output voltage disconnect during shutdown. The LTC3779 is available in a 38-lead TSSOP package with additional pin spacing for high voltage operation. Two operating junction temperature grades are available, with extended and industrial versions from –40 to 125°C and a high temperature automotive version from –40°C to 150°C. Pricing starts at $5.95 each in 1,000-piece quantities.