Electronic Design

Ultra-Quiet Buck Converter Suits RF And High-Speed Data Applications

The most challenging realm for dc-dc converters comprises cell-phone data cards, backplane adapters, and other applications that are sensitive to radiated and conducted switching noise from the converter. Enpirion, the Lucent spinoff with a converter technology that integrates the FETs and places the inductor inside the package, has quietly captured a large share of that kind of business in the last couple of years.

Housed in a 3- by 3-mm QFN package, Enpirion’s 600-mA EP5368QI synchronous buck regulator has the lowest output ripple yet at any given output level (see the figure). Because target applications present a more or less steady load, the EP5368QI is a basic pulse-width modulation (PWM) switcher with soft-start, but it runs at 4 MHz. Compensation is internal. The only external components necessary are two multilayer ceramic chip (MLCC) capacitors, one on VIN and one on VOUT.

Preset output voltages from 0.8 to 3.3 V are programmable via a three-pin selection scheme. Other voltages can be set via an external divider. Maximum output with just two external capacitors is 600 mA, but that can be extended to 700 mA with the addition of a few more components. Shut-down current is 0.75 µA. Available now, the EP5368QI costs $1.25 in lots of 10,000.


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