19-5732; Rev 2; 8/11
IEEE 802.3af/at-Compliant, Powered Device Interface
Controllers with Integrated Power MOSFET
The MAX5981 provides a complete interface for a pow-
ered device (PD) to comply with the IEEE® 802.3af/at
standard in a power-over-ethernet (PoE) system. The
MAX5981 provides the PD with a detection signature,
classification signature, and an integrated isolation
power switch with inrush current control. During the
inrush period, the MAX5981 limits the current to less
than 180mA before switching to the higher current limit
(720mA to 880mA) when the isolation power MOSFET is
fully enhanced. The device features an input UVLO with
wide hysteresis and long deglitch time to compensate for
twisted-pair cable resistive drop and to assure glitch-free
transition during power-on/-off conditions. The MAX5981
can withstand up to 100V at the input.
The MAX5981 supports a 2-Event classification method
as specified in the IEEE 802.3at standard and provides a
signal to indicate when probed by a Type 2 power sourc-
ing equipment (PSE). The device detects the presence
of a wall adapter power source connection and allows
a smooth switch over from the PoE power source to the
wall power adapter.
The MAX5981 also provides a power-good (PG) signal,
two-step current limit and foldback, overtemperature
protection, and di/dt limit. A sleep mode feature in
the MAX5981 provides low power consumption while
supporting Maintain Power Signature (MPS). An ultra-
low-power sleep mode feature in the MAX5981 further
reduces power consumption while still supporting MPS.
The MAX5981 also features an LED driver that is auto-
matically activated during sleep mode. During sleep
mode, the LED driver sources a periodic current (ILED) at
250Hz (MAX5981A) or 15.625kHz (MAX5981B).
The MAX5981 is available in a 16-pin, 5mm x 5mm TQFN
power package. The device is rated over the -40°C to
+85°C extended temperature range.
S Sleep Mode and Ultra-Low Power
S IEEE 802.3af/at Compliant
S 2-Event Classification or an External Wall Adapter
S Simplified Wall Adapter Interface
S PoE Classification 0–5
S 100V Input Absolute Maximum Rating
S Inrush Current Limit of 180mA Maximum
S Current Limit During Normal Operation Between
720mA and 880mA
S Current Limit and Foldback
S Legacy UVLO at 36V
S LED Driver with Programmable LED Current
S Overtemperature Protection
S Thermally Enhanced, 5mm x 5mm, 16-Pin TQFN
IEEE 802.3af/at Powered Devices
IP Phones, Wireless Access Nodes, IP Security
WiMAXK Base Stations
MAX5981AETE+ -40NC to +85NC 16 TQFN-EP*
MAX5981BETE+ -40NC to +85NC 16 TQFN-EP*
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
WiMAX is a trademark of WiMAX Forum.
IEEE is a registered service mark of the Institute of Electrical
and Electronics Engineers, Inc.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.