Power Electronics

60V Input Synchronous Step-Down DC/DC Controller

Linear Technology Corporation introduces the LTC3891, a high voltage synchronous step-down DC/DC controller that draws only 50µA in standby mode with the output in regulation. The 4V to 60V input supply range is designed to protect against high voltage transients, continue operation during automotive cold crank and cover a broad range of input sources and battery chemistries. The output voltage can be set from 0.8V to 24V at output currents up to 20 amps with efficiencies as high as 95%, making it well suited for 12V, 24V or 48V automotive, heavy equipment, industrial control, robotics and telecom applications.

The LTC3891 has powerful 1.1Ohm on-chip MOSFET gate drivers. It operates with a selectable fixed frequency between 50kHz and 900kHz and is synchronizable to an external clock from 75kHz to 850kHz with its phase-locked loop (PLL). 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 excellent 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 95ns 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.

The LTC3891 is available in 20-pin 3mm x 4mm QFN and 20-lead TSSOP thermally enhanced packages. Three operating junction temperature grades are available with extended and industrial versions from -40 to 125°C, a high temp automotive grade version from -40°C to 150°C and a military grade version from -55°C to 150°C. The 1,000-piece price starts at $3.47 each

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