DC/DC controller eliminates external surge protection devices

5th March 2018

Analog Devices

Lanna Deamer

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Datasheet

Analog Devices has announced the Power by Linear LTC7810, a high voltage non-isolated dual output synchronous step-down DC/DC controller that drives all N-channel MOSFET power stages. Its 4.5-140V (150V abs max) input voltage range is designed to operate from a high input voltage or from an input that has high voltage surges, eliminating the need for external surge suppression devices.

The LTC7810 operates at up to 100% duty cycle during input voltage dips down to 4.1V, suitable for transportation, industrial, robotic and datacom applications.

The output voltage can be set from 1-60V at output currents up to at least 20A per channel with efficiencies as high as 96%. This part draws only 16µA in sleep mode from a 48V input while regulating outputs at 12V and 3.3V, well suited for always-on systems. An internal charge pump allows for 100% duty cycle operation in dropout, a useful feature when powered from a battery during discharge.

Optional spread spectrum reduces radiated and conducted emissions. The LTC7810’s powerful 1Ω N-channel MOSFET gate drivers can be programmed to 6, 8 or 10V to enable the use of logic-level or standard-threshold MOSFETs to maximise efficiency.

To prevent high on-chip power dissipation in high input voltage applications, the LTC7810 can drive the gate of an optional external N-channel MOSFET, acting as a low dropout linear regulator, to supply IC power.

The EXTV_CC pin permits the LTC7810 to be powered from the output of the regulator or another available source, further reducing power dissipation and improving efficiency.

The LTC7810 operates with a selectable fixed frequency between 50-750kHz and is synchronisable to an external clock from 75-720kHz. The user can select from forced continuous operation, pulse-skipping or low ripple Burst Mode operation during light loads. Its current mode architecture provides easy loop compensation, fast transient response and excellent line regulation.

Current sensing is accomplished by measuring the voltage drop across the output inductor (DCR) for highest efficiency or by using an optional sense resistor. A low 90ns minimum on-time allows for high step-down ratios at high switching frequency. Current foldback limits MOSFET heat dissipation during overload conditions.

Additional features include adjustable input overvoltage lockout and soft-start. The LTC7810 is available in a 48-lead 7x7mm eLQFP thermally enhanced package with no connect pins for high voltage spacing. Two operating junction temperature grades are available with extended and industrial versions from -40°C to 125°C and a high temp automotive version from -40°C to 150°C.