60V Synchronous Step-Up DC/DC Controller
Linear Technology Corporation announces the LTC3786, a synchronous step-up DC/DC controller that replaces the boost diode with a high efficiency N-channel MOSFET. This eliminates the heat sink normally required in medium to high power boost converters. In applications where the input voltage may exceed the regulated output voltage, the LTC3786 is able to keep the synchronous MOSFET on continuously so that the output voltage follows the input voltage with minimal power loss. The LTC3786's low 55μA quiescent current extends the run time in battery-powered applications when in standby mode. This controller can produce a 24V at 5A output from a 12V input with up to 98% efficiency, making it ideal for automotive, industrial, and medical applications where a step-up DC/DC converter must have low heat dissipation in a small solution size. The LTC3786 operates from an input voltage ranging from 4.5V to 38V during start-up, maintaining operation down to 2.5V after start-up and can regulate an output voltage as high as 60V. The powerful 1.2 Ohm onboard N-channel MOSFET gate drivers are capable of slewing large MOSFET gates quickly, minimizing transition losses and allowing for up to a 10A output current. The LTC3786 has adjustable cycle-by-cycle current limit protection and uses either a sense resistor or monitors the voltage drop across the inductor (DCR) for current sensing. The LTC3786 has a phase-lockable switching frequency range of 75kHz to 850kHz and a fixed frequency operating range from 50kHz to 900kHz. Furthermore, the LTC3786 has adjustable soft-start and maintains ±1% reference voltage accuracy over an operating temperature range of -40°C to 125°C. Summary of Features: LTC3786 • Up to 98% Efficiency • Eliminates Heat Sink in Medium to High Power Boost Converters • Up to 60V VOUT Operation • Wide VIN Ranging from 4.5V to 38V, Maintains Operation down to 2.5V After Start-Up • Low 55μA Quiescent Current Extends the Run-Time in Battery-Powered Applications • 8μA Shut Down Current • Powerful 1.2 Ohm Gate Drivers • 100% Duty Cycle Capability for Synchronous MOSFET • Phase Lockable Frequency from 75kHz to 850kHz • Programmable Fixed Frequency from 50kHz to 900kHz • RSENSE or Inductor DCR Current Sensing • Current Mode Control • ±1% Reference Voltage Accuracy over -40oC to +125oC • Programmable Soft-Start • Power Good Output The LTC3786 is available in a thermally enhanced MSOP-16 package and a 3mm x 3mm QFN. For more information, visit www.linear.com/3786
Linear Technology Corporation introduced 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. Summary of Features: LTC3891 • Wide Input Voltage Range: 4V to 60V • 50μA Quiescent Current • Wide Output Voltage Range: 0.8V to 24V • Synchronous Rectification for up to 95% Efficiency • Low 95ns Minimum On-time for High Step-Down Ratios • DCR or RSENSE Current Sense • Selectable Low Ripple Burst Mode® Operation, Pulse Skipping or Continuous Operation • Selectable Fixed Operating Frequency from 50kHz to 900kHz • PLL Synchronizable Operating Frequency from 75kHz to 850kHz • Current-Mode Control for Fast Transient Response & Easy Loop Compensation • Adjustable Soft-Start or Tracking • Output Overvoltage & Overcurrent Foldback Protection • Extended & Industrial Grades: -40°C to 125°C Operating Junction Temp • Automotive Temp Grade: -40°C to 150°C Operating Junction Temp • Military Temp Grade: -55°C to 150°C Operating Junction Temp 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. For more information, visit www.linear.com/3891. www.linear.com
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