Linear Technology LTC3891 high-voltage synchronous step-down DC/DC controller

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Linear Technology has introduced the LTC3891, a high-voltage synchronous step-down DC/DC controller that draws 50 µA in standby mode with the output in regulation.

The 4 to 60 V input is designed to protect against high-voltage transients, continue operation during motor vehicle cold crank and cover a broad range of input sources and battery chemistries. The output voltage can be set from 0.8 to 24 at output currents up to 20 A with efficiencies to 95%, making it suitable for 12, 24 or 48 V motor vehicle, heavy equipment, industrial control, robotics and telecom applications.

It has 1.1 Ω on-chip MOSFET gate drivers and operates with a selectable fixed frequency between 50 and 900 kHz and is synchronisable to an external clock from 75 to 850 kHz with its phase-locked loop.

The user can select from continuous operation, pulse skipping and low ripple Burst Mode operation during light loads. Its current-mode architecture provides easy loop compensation, fast transient response and good line regulation.

Output current sensing is accomplished by measuring the voltage drop across the output inductor (DCR) for the highest efficiency or by using an optional sense resistor. Current foldback limits MOSFET heat dissipation during overload conditions.

Additional features include a low 95 ns minimum on-time for high step-down ratios at high frequency, up to 99% duty cycle for low-voltage drop-out, an internal LDO that powers gate drivers from the input voltage or EXTVCC and a power good signal.