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The MAX8764 pulse-width modulation (PWM) controller
provides high efficiency, excellent transient response,
and high-DC output accuracy needed for stepping
down high-voltage batteries to generate low-voltage
CPU core or chipset/RAM supplies in notebook computers.
Maxim's proprietary Quick-PWM™ quick-response,
constant-on-time PWM control scheme handles wide
input/output voltage ratios with ease and provides
100ns "instant-on" response to load transients while
maintaining a relatively constant switching frequency.
Efficiency is enhanced by an ability to drive very large
synchronous-rectifier MOSFETs. Accurate current sensing
to ensure reliable overload protection is available
using an external current-sense resistor in series with
the synchronous rectifier. Alternatively, the synchronous
rectifier itself can be used for less-accurate current
sensing at the lowest possible power dissipation. A
high-output impedance in shutdown eliminates negative
output voltages, saving the cost of a Schottky diode
on the output.
Single-stage buck conversion allows the MAX8764 to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, two-stage conversion
(stepping down the 5V system supply instead of the
battery) at a higher switching frequency allows the minimum
possible physical size.
The MAX8764 is intended for CPU core, chipset,
DRAM, or other low-voltage supplies as low as 1V. It is
available in 20-pin QSOP and thin QFN packages and
includes both adjustable overvoltage and undervoltage
protection.
For a dual step-down PWM controller with accurate current
limit, refer to the MAX8743 data sheet. The
MAX1714/MAX1715 single/dual PWM controllers are
similar to the MAX8764, but do not use current-sense
resistors.
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