Synchronous Buck-Boost Controller Integrates Switching Bias Supply

Analog Devices’ Power by Linear LTC3777, 150V four-switch synchronous buck-boost DC/DC controller operates from input voltages above, below, or equal to the regulated output voltage. Its 4.5V to 150V input voltage range operates 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 medical applications.

 

To prevent high on-chip power dissipation in high input voltage applications, the LTC3777 integrates a low quiescent current high efficiency switching bias supply for its internal power consumption. Output voltage can be set from 1.2V to 150V at output currents up to tens of amps, depending on the choice of external components. Output power up to 500W can be delivered with a single device. Higher powers can be achieved when multiple circuits are configured in parallel. The device’s 1.5Ω N-channel MOSFET gate drivers can be adjusted from 6V to 10V, enabling the use of logic-level or standard-threshold MOSFETs.

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The LTC3777 employs a proprietary current mode control architecture for constant frequency in buck, boost or buck-boost modes. The operating frequency can be synchronized to an external clock from 50 kHz to 600 kHz, while an input/output constant current loop provides support for battery charging and overload protection. The user can select either forced continuous mode or discontinuous mode to maximize light load efficiency. Additional features include seamless transfers between operating regions, a power good output voltage monitor, adjustable soft-start and input overvoltage lockout, and output voltage disconnect during shutdown.

 

The LTC3777 is available in a 48-lead e-LQFP package with pin skipping for high voltage spacing. Extended and industrial versions are available from -40 to 125°C. For more specs, peruse the LTC3777 datasheet.