Synchronous four-switch buck-boost controller suits transport and medical use

A 150V high efficiency four-switch synchronous buck-boost DC/DC controller, the LTC3777, by Analog Devices operates from input voltages above, below or equal to the regulated output voltage and had an efficiency of up to 99 per cent.

The Power by Linear DC/DC controller has an input voltage of 4.5 to 150V and operates from a high input voltage source or from an input that has high voltage surges, eliminating the need for external surge suppression devices. This, says Analog Devices, makes it suitable for transportation, industrial and medical

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. The output voltage of the LTC3777 can be set from 1.2 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 LTC3777’s 1.5-Ohm n-channel MOSFET gate drivers can be adjusted from 6.0 to 10V, enabling the use of logic-level or standard-threshold MOSFETs.

The LTC3777 employs a proprietary current mode control architecture for constant frequency in buck, boost or buck-boost modes. The operating frequency can be synchronised to an external clock from 50 to 600kHz, while an I/O constant current loop provides support for battery charging and over-load protection. The user can select either forced continuous mode or discontinuous mode to maximise light load efficiency. There are also 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 7.0 x7.0mm e-LQFP package with pin skipping for high voltage spacing. Extended and industrial versions are available from –40 to +125 degree C.

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