150V synchronous step-down DC/DC controller eliminates external surge protection devices

A high voltage non isolated synchronous step-down switching regulator controller from Linear Technology drives an all N-channel MOSFET power stage.

Accepting an input ranging from 4 to 140V, the part is designed to operate either from a high input voltage source or from an input that has high voltage surges. This, the company continues, eliminates the need for external surge suppression devices.

The LTC3895 continues to operate at up to 100% duty cycle during input voltage dips down to 4V, making it suited for applications in the transportation, industrial control, robotic and datacom sectors.

The output voltage can be set from 0.8 to 60V, with currents of up to 20A and efficiencies as high as 96%. Drawing 40µA in sleep mode with the output voltage in regulation, the part can be used in always on systems. An internal charge pump allows for 100% duty cycle operation in dropout, while the LTC3895’s 1O N-channel MOSFET gate drivers can be adjusted from 5V to 10V to enable the use of logic- or standard-level MOSFETs.

To prevent high on-chip power dissipation in high input voltage applications, the LTC3895 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 power. The LTC3895 can also be powered from the output of the switching regulator or other available source, reducing power dissipation and improving efficiency.

The LTC3895 is available in a TSSOP-38 thermally enhanced package with several pins removed for high voltage spacing. Two operating junction temperature grades are available: extended and industrial versions from -40 to 125°C; and an automotive version from -40 to 150°C