40-V, 1-A synchronous buck converter steps 36-VIN down to 3.3-VOUT with a 2-MHz switching frequency

January 08, 2013 // By Paul Buckley
Linear Technology has unveiled a 40 V input capable synchronous buck converter than can deliver up to 1 A of continuous output current from a 3 mm x 4 mm DFN-14 (or thermally enhanced MSOP16) package.

The LTC3646 operates from an input voltage range of 4 V to 40 V, making it ideal for automotive and industrial applications that require high voltage input capability, high efficiency and fast switching frequencies for small solution footprints.

The device utilizes a controlled on-time architecture that can step inputs as high as 36 V down to 3.3 V with switching frequencies in excess of 2 MHz, keeping switching noise out of critical frequency bands, such as AM radio. Furthermore, it can deliver very fast transient response even with duty cycles less than 10%. Its internal synchronous rectification delivers efficiencies as high as 95% and requires only 140 µA of quiescent current, maximizing battery run time. The combination of its 3 mm x 4 mm DFN package (or MSOP-16E) and tiny externals, offers a compact solution footprint for a wide array of high voltage applications.

The LTC3646 utilizes internal high-side and synchronous power switches to deliver high efficiency outputs up to 1 A. Its internal switching frequency can be programmed between 200 kHz and 3.0 MHz or synchronized to an external clock. The combination of high efficiency and only 140 µA of quiescent current offers high efficiency over a very broad load range. For noise sensitive applications, the LTC3646 can be used in forced continuous operation to minimize voltage ripple.

The standard LTC3646 offers an output range of 2.0 V to 30 V whereas the LTC3646-1 offers outputs from 0.6 V to 15 V. Both versions offer additional features including internal soft-start, internal compensation and robust short-circuit protection.

Availability and Pricing

Pricing for both packages, the LTC3646EDE/-1 and LTC3646EMSE/-1, respectively, starts at $2.85 each. Extended temperature versions (I grades), namely the LTC3646IDE/-1 and LTC3646IMSE/-1, are available with pricing starting at $3.14 each.  Finally, high temperature (H grade) options, namely the LTC3646HDE/-1 and LTC3646HMSE/-1 are available with pricing starting at $3.39 each. All pricing is in 1,000-piece quantities and all versions are