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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