Low IQ, 60V input synchronous step-down controller

February 24, 2014 // By Graham Prophet
LT3840 is a wide-range synchronous step-down DC/DC controller which includes a 7.5V buck-boost bias voltage to provide efficient gate drive over a 2.5V to 60V input voltage range. The LT3840 generates a 7.5V bias voltage for MOSFET gate drive regardless of whether the input voltage is above, below or equal to 7.5V. The 2.5V to 60V supply range is designed to protect against high voltage transients and continuing operation during automotive cold crank, as well as covering a broad range of input sources and battery chemistries.

It draws only 75µA when regulating the output voltage with no load, extending the run time in battery-powered applications. The output voltage can be set from 1.25V to 60V at output currents up to 30A with efficiencies as high as 95%, making it suitable for 12V or 24V automotive, heavy equipment, industrial control, robotics and telecom applications. Accurate current regulation is achieved with the LT3840 programmable current limit while the current monitor function reports the average output current. The user can select from continuous operation, pulse skipping and low ripple Burst Mode operation during light loads.

The LT3840 has powerful on-chip gate drivers for driving multiple standard or logic level N-channel MOSFETs. It operates with a selectable fixed frequency between 50 kHz and 1 MHz or can be synchronisable to an external clock over the same range. Its current-mode architecture provides easy loop compensation, fast transient response and good line regulation. Additional features include up to 99% duty cycle for low voltage dropout, accurate over-and undervoltage lockouts, soft-start/tracking and a power good signal.

The LT3840 is available in 28-lead TSSOP and 4 x 6 mm QFN-38 thermally enhanced packages in industrial, automotive or military temperature grades, priced from $3.65 (1000).

Linear Technology; www.linear.com/product/LT3840