The MLP 8x8 power package extends
the concept of enhanced packaging. The
integrated FDMF8700 module provides
an additional efficiency gain of 1.5% to 2% for peak- and steadypower
levels compared with discrete solutions using D-Pak packaging.
The complete Fairchild family of DrMOS multichip modules
includes the FDMF6700, FDMF8704, FDMF8704V, and
FDMF8705 (Fig. 3).
Renesas Technology America’s R2J20602NP integrates a driver
IC and high- and low-side power MOSFETs in a 56-pin quad flat
no-lead (QFN) package that conforms to the integrated DrMOS
package standard. This second-generation driver-MOSFET product
operates at up to a 2-MHz switching frequency and has a maximum
output current of 40 A. Operating at 1 MHz with VIN = 12 V
and VOUT = 1.3 V, it achieves a maximum efficiency of approximately
89%. With an output current of 25 A, power loss is only 4.4 W.
The R2J20602NP complies with the European Union’s
Restrictions on Hazardous Substances (RoHS) and with the
DrMOS standard. Its high heat-radiation package offers a small
(8 by 8 mm) mounting area. It also uses a wireless copper-plate
construction technique for internal connections, reducing resistance
and parasitic inductance within the package. Pins for largecurrent
paths occupy most of the rear surface of the package and
facilitate heat dissipation.
The NXP PIP212-12M also meets the DrMOS spec. It consists
of a high side (control FET), a low side (synchronous FET),
and a FET driver. The fully integrated device comes in a single
surface-mount package with integral heatsink. It employs highperformance
MOSFETs and a customized driver that monitors
switching dead time and actively eliminates dead time without
allowing the devices to go into cross conduction.
Its feature set includes functionality for sequencing. An onboard
regulator provides 5 V in 12-V-only applications. Its built-in
loss phase-detection circuitry suits multiphase applications. And,
its VOUT sense allows current sense back to the PWM as well as multiphase current-sharing designs. With its integrated design,
it can be used as the building block of buck regulators capable of
greater than 30 A per phase and frequencies of up to 1 MHz per
phase. Moreover, greater power densities are possible than with
discrete solutions or previous integrated solutions.
MULTIPHASE PWM ICS
Semtech’s SC2447 is a high-frequency, dual-phase, PWM stepdown
controller optimized for Philips and Renesas DrMOS. Both
phases can source or sink load currents, suiting the SC2447 for
networking system power. It uses fixed-frequency, continuousconduction
peak current-mode control for good compensation
and fast transient response.
The SC2447 generates two independent, 180° out-of-phase,
30-A outputs. Either inductor dc resistance or a precision sense
resistor can be used for current-mode control. Inductor dc resistance
sensing has the advantage of being lossless. Each phase has
an individual closed-loop soft-start and overload shutdown timer.
Intersil’s ISL6307A controls microprocessor core voltage regulation
by driving from two to six synchronous-rectified buck channels
in parallel (Fig. 3, again). Microprocessor loads can generate
load transients with extremely fast edge rates. The ISL6307A
features a high-bandwidth control loop and ripple frequencies up
to 12 MHz to provide optimal response to the transients.
The ISL6307A senses current by utilizing patented techniques
to measure the voltage across the RDS(ON) of the lower MOSFETs
or dc resistance (DCR) of the output inductor during the lower
MOSFET conduction intervals. Current sensing provides the
needed signals for precision droop, channel-current balancing, and
overcurrent protection. A programmable internal temperature
compensation function compensates for the temperature coefficient
of the current-sense element.