MAX5922 Datasheet, PDF (1/21 Pages) Maxim Integrated Products – +48V, Single-Port Network Power Switch For Power-Over-LAN

19-2708; Rev 0; 4/03
+48V, Single-Port Network Power Switch
For Power-Over-LAN
General Description
The MAX5922A/B/C is a single-port network power con-
troller 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 nec-
essary 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 nec-
essary 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 detec-
tion 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 suc-
cessfully 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 inte-
grated 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, and FAULT status sig-
nals to indicate output power is good, zero-current fault,
and other faults (overcurrent, overtemperature), respec-
tively. The MAX5922 is available in a 28-pin TSSOP pack-
age and is rated over the extended -40°C to +85°C
temperature range.
Features
o IEEE 802.3af Compliant
o +32V to +60V Wide Operating Input Range
o 0.45Ω Integrated Power Switch
o Power Device (PD) Detection and Classification
o 100µA PD Leakage Detection Tolerant
o Programmable Current Limit
o Zero-Current Detection with Status Output
o Detection Collision Avoidance Option for Midspan
Application
o Input Logic Signals Compatible with 1.8V to 5V
CMOS Logic
o Separate Analog and Digital Grounds with Up to
±4V Offset
o Power-Good Status Output
o Overcurrent and Overtemperature Protection with
Status Outputs
o Current-Limit Foldback with Timeout and Duty-
Cycle Control
o Latch or Autorestart Fault Management
Ordering Information
PART
MAX5922AEUI
MAX5922BEUI
MAX5922CEUI
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 TSSOP
28 TSSOP
28 TSSOP
Applications
Power-Sourcing Equipment (PSE)
Power-Over-LAN/Power-Over-MDI
(Media-Dependent Interface)
Computer Telephony
Single-Port Power Injector/Adapter
Midspan Power Injector
Switches/Routers with In-Line Power
Typical Application Circuits, Selector Guide, and Pin
Configuration appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
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