Four switch controller integrates bias supply

February 12, 2018 // By Nick Flaherty
Analog Devices has launched a 150V high efficiency 4-switch synchronous buck-boost DC/DC controller, which operates from input voltages above, below or equal to the regulated output voltage.

The 4.5V to 150V input voltage range of the LTC3777 operates from a high input voltage source or from an input that has high voltage surges, eliminating the need for external surge suppression devices in transportation, industrial and medical applications with an output power up to 500W.

To prevent high on-chip power dissipation in high input voltage applications, the LTC3777 integrates a low quiescent current 99% efficiency switching bias supply for its internal power consumption. The output voltage of the LTC3777 can be set from 1.2V to 50V at output currents up to tens of amps, depending on the choice of external components. 

The 1.5Ω N-channel MOSFET gate drivers can be adjusted from 6V to 10V, enabling the use of logic-level or standard-threshold MOSFETs and the device uses 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 50kHz to 600kHz, 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 and is priced at $8.40 in 1,000 quantities . Extended and industrial versions are available from –40 to 125°C.

www.linear.com/product/LTC3777