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Dc-dc compensates for PCB traces

Posted: 14 Jan 2005 ?? ?Print Version ?Bookmark and Share

Keywords:linear technology? ltc3709? dc-dc controller? pcb?

Linear Technology Corp.'s LTC3709 is a two-phase step-down synchronous dc-dc controller with a true differential amplifier at the output that eliminates voltage-drop errors introduced by a PCB's traces and high load currents. It also rejects common-mode signals that are capacitively or inductively coupled into the feedback pin through the board's traces.

Suited to servers, large memory arrays, industrial single-board computers and control systems, the LTC3709, with suitable external (n-channel) power MOSFETs, is designed to deliver up to 40A at as low as 0.6V with the fewest input and output capacitors. With an on-time of 100ns, the LTC3709 responds very quickly to load transients.

This regulator, which works from a 4V to 30V input, features a constant on-time, current-mode architecture that delivers very low duty cycles (down to 2 percent) without the need for a sense resistor. Users select operating frequency (nominally, 200kHz) with an external resistor. Options include remote sensing (with sense resistors) to optimize current balancing. A TRACK input pin for sequencing is available for proper startup for systems with multiple dc-dc regulators (LTC3709's output voltage tracks the output of other regulators in coincident or ratiometric fashion). The chip can be synchronized to an external clock.

The IC offers fault protection against output over-voltage and short-circuit conditions. Rated for operation over the -40C to 85C temperature range, its available in a 5-by-5mm QFN as well as a 36-lead SSOP. Pricing starts at $4.90 each in 1,000 pieces.

- Vincent Biancomano


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