The MAX5953A/MAX5953B/MAX5953C/MAX5953D
integrate a complete power IC solution for Powered
Devices (PD) in a Power-Over-Ethernet (PoE) system, in
compliance with the IEEE 802.3af standard. The
MAX5953A/MAX5953B/MAX5953C/MAX5953D provide
the PD with a detection signature, a classification signature,
and an integrated isolation switch with programmable
inrush current control. These devices also
integrate a voltage-mode PWM controller with two
power MOSFETs connected in a two-switch voltage-clamped
DC-DC converter configuration.
An integrated MOSFET provides PD isolation during
detection and classification. All devices guarantee a
leakage current offset of less than 10µA during the
detection phase. A programmable current limit prevents
high inrush current during power-on. The devices
feature power-mode undervoltage lockout (UVLO) with
wide hysteresis and long deglitch time to compensate
for twisted-pair-cable resistive drop and to assure
glitch-free transition between detection, classification,
and power-on/-off phases. The MAX5953A/MAX5953C
have an adjustable UVLO threshold with the default
value compliant to the 802.3af standard, while the
MAX5953B/MAX5953D have a lower and fixed UVLO
threshold compatible with some legacy pre-802.3af
power-sourcing equipment (PSE) devices.
The DC-DC converters are operable in either forward or
flyback configurations with a wide input voltage range
from 11V to 76V and up to 15W of output power. The
voltage-clamped power topology enables full recovery
of stored magnetizing and leakage inductive energy for
enhanced efficiency and reliability. When using the
high-side MOSFET, the controller can be configured as
a buck converter. A look-ahead signal for driving secondary-side synchronous rectifiers can be used to
increase efficiency. A wide array of protection features
include UVLO, over-temperature shutdown, and short-circuit
protection with hiccup current limit for enhanced
performance and reliability. Operation up to 500kHz
allows for smaller external magnetics and capacitors.
The MAX5953A/MAX5953B/MAX5953C/MAX5953D are
available in a high-power (2.22W), 7mm x 7mm thermally
enhanced thin QFN package.
Notes: **This pricing is BUDGETARY, for comparing similar parts. Prices are in
U.S. dollars and subject to change. Quantity pricing may vary
substantially and international prices may differ due to local
duties, taxes, fees, and exchange rates. For volume-specific prices
and delivery, please see the price and availability page
or contact an authorized distributor.
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