The MAX8743 is a dual pulse-width modulation (PWM)
controller configured for step-down (buck) topologies
that provides the high efficiency, excellent transient
response, and high DC output accuracy necessary for
stepping down high-voltage batteries to generate lowvoltage
chipset and RAM power supplies in notebook
computers. The CS_ inputs can be used with low-side
sense resistors to provide accurate current limits or can
be connected to LX_, using low-side MOSFETs as current-
sense elements. High output impedance in shutdown
eliminates negative output voltages, saving the
cost of a Schottky diode at the output.
The on-demand PWM controllers are free running, constant
on-time with input feed-forward. This configuration
provides ultra-fast transient response, wide input-output
differential range, low supply current, and tight load-regulation
characteristics. The MAX8743 is simple and easy
to compensate.
Single-stage buck conversion allows the MAX8743 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 MAX8743 is intended for generating chipset, DRAM,
CPU I/O, or other low-voltage supplies down to 1V. The
MAX8743 is available in 28-pin QSOP and 36-pin thin
QFN packages.
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