The MAX5922A/B/C is a single-port network power controller
with an integrated power MOSFET, operating from
a +32V to +60V supply rail. The device is specifically
designed for power-sourcing equipment (PSE) in power-over-LAN
applications and is fully compliant to the IEEE®
802.3af standard. The MAX5922 provides power devices
(PD) discovery, classification, current limit, and other necessary
functions for an IEEE 802.3af compliant PSE.
The MAX5922 is suitable for PSE function in both
switch/router systems where the power is delivered to the
load through the signal pairs, and in midspan systems
where the power is delivered to the load through the
spare pairs. In midspan mode, a detection collision
avoidance circuit (MAX5922A/C only) provides the necessary
back-off timing to prevent fault detections that
happen when two different PSEs try to detect and
power the same PD. The MAX5922B/C have a detection
disable input that can be connected high to disable
the detection/classification functions or connected low
to enable them.
The MAX5922 features a programmable undervoltage
lockout (UVLO) that keeps the device in shutdown until
the input voltage exceeds a certain threshold, set to 38V
(MAX5922A) or 28V (MAX5922B/C) internally. After successfully
discovering and classifying a PD, the MAX5922
enters startup mode. During startup, the MAX5922 limits
the output voltage and current slew rate to minimize EMI
(electromagnetic interference). The MAX5922 has an integrated
0.45Ω N-channel power MOSFET that provides
efficient operation and simplified system design. The
MAX5922 monitors and provides current-limit protection
to the load at all times. The current limit is programmable
using an external current-sensing resistor. The MAX5922
features current-limit foldback and duty-cycle limit to
ensure robust operation during load-fault and short-circuit
conditions. Fault management allows the part to either
latch-off or autorestart after a fault.
The MAX5922 provides POK, ZC-bar, and active-low FAULT status signals
to indicate output power is good, zero-current fault,
and other faults (overcurrent, overtemperature), respectively.
The MAX5922 is available in a 28-pin TSSOP package
and is rated over the extended -40°C to +85°C
temperature range.
Key Features
Applications/Uses
IEEE 802.3af Compliant
+32V to +60V Wide Operating Input Range
0.45Ω Integrated Power Switch
Power Device (PD) Detection and Classification
100µA PD Leakage Detection Tolerant
Programmable Current Limit
Zero-Current Detection with Status Output
Detection Collision Avoidance Option for Midspan
Application
Input Logic Signals Compatible with 1.8V to 5V
CMOS Logic
Separate Analog and Digital Grounds with Up to
+4V Offset
Power-Good Status Output
Overcurrent and Overtemperature Protection with
Status Outputs
Current-Limit Foldback with Timeout and Duty-Cycle Control
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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