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IEEE 802.3af/at-Compliant, Powered Device Interface

Controllers with Integrated Power MOSFET

MAX5981A/MAX5981B

_______________________________________________________________ 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.

General Description

The MAX5981 provides a com plete 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,

classifica tion 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 cur rent 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 condi tions. The MAX5981

can with stand 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 fold back, 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 consump tion 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 peri odic current (I

LED

) 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.

Features

S Sleep Mode and Ultra-Low Power

S IEEE 802.3af/at Compliant

S 2-Event Classification or an External Wall Adapter

Indicator Output

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

Applications

IEEE 802.3af/at Powered Devices

IP Phones, Wireless Access Nodes, IP Security

Cameras

WiMAXK Base Stations

19-5732; Rev 2; 8/11

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

Ordering Information

WiMAX is a trademark of WiMAX Forum.

IEEE is a registered service mark of the Institute of Electrical

and Electronics Engineers, Inc.

PART TEMP RANGE

PIN-

PACKAGE

SLEEP

MODE

MAX5981AETE+

-40NC to +85NC

16 TQFN-EP* Yes

MAX5981BETE+

-40NC to +85NC

16 TQFN-EP* Yes

Summary of content (16 pages)

PAGE 1
9-5732; 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 powered 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.
PAGE 2
MAX5981A/MAX5981B IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET ABSOLUTE MAXIMUM RATINGS VDD to VSS...........................................................-0.3V to +100V DET, RTN, WAD, PG, 2EC to VSS........................ -0.3V to +100V CLS, SL, WK, ULP, LED to VSS. ..............................-0.3V to +6V Maximum Current on CLS (100ms maximum)..................100mA Continuous Power Dissipation (TA = +70NC) (Note 1) TQFN (derate 28.
PAGE 3
IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET (VIN = (VDD - VSS) = 48V, RDET = 24.9kω, RCLS = 615ω, and RSL = 60.4kω. RTN, WAD, PG, 2EC, WK, and ULP unconnected, all voltages are referenced to VSS, unless otherwise noted. TA = TJ = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 3) MIN TYP MAX UNITS VIN Turn-On Voltage PARAMETER VON VIN rising 34.3 35.4 36.
PAGE 4
MAX5981A/MAX5981B IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET ELECTRICAL CHARACTERISTICS (continued) (VIN = (VDD - VSS) = 48V, RDET = 24.9kω, RCLS = 615ω, and RSL = 60.4kω. RTN, WAD, PG, 2EC, WK, and ULP unconnected, all voltages are referenced to VSS, unless otherwise noted. TA = TJ = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC.) (Note 3) PARAMETER SYMBOL CONDITIONS MIN LED Current Programmable Range 10 20.
PAGE 5
IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET SIGNATURE RESISTANCE vs. INPUT VOLTAGE 25.5 RSIGNATURE (kI) IIN (mA) 0.3 0.2 TA = -40NC 25.0 TA = +25NC 24.5 0.1 TA = +85NC 4 2 0 2 4 6 8 TA = +25NC -2 -4 2 0 10 TA = +85NC 0 24.0 0 TA = -40NC MAX5981 toc03 IIN = IVDD + IDET RDET = 24.9kI RTN = 2EC = PG = WAD = VDD INPUT OFFSET CURRENT (FA) IIN = IVDD + IDET RDET = 25.4kI RTN = 2EC = PG = WAD = VDD -40°C P TA P +85NC 0.4 26.
PAGE 6
Typical Operating Characteristics (continued) (VIN = (VDD - VSS) = 54V, RDET = 24.9kω, RCLS = 615ω, and RSL = 60.4kω. RTN, WAD, PG, 2EC, WK, and ULP unconnected; all voltages are referenced to VSS.) INRUSH CONTROL WAVEFORM WITH TYPE 2 CLASSIFICATION NORMAL OPERATION CURRENT LIMIT vs.
PAGE 7
IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET 2 DET 3 I.C. 4 ULP WK SL LED 13 + MAX5981A MAX5981B EP* 5 6 7 8 RTN VDD 14 RTN 1 15 VSS N.C. 16 VSS TOP VIEW 12 CLS 11 2EC 10 PG 9 WAD TQFN CONNECT TO VSS. Pin Description PIN NAME 1 N.C. No Connection. Not internally connected. FUNCTION 2 VDD 3 DET Positive Supply Input. Connect a 68nF (min) bypass capacitor between VDD and VSS. Detection Resistor Input.
PAGE 8
MAX5981A/MAX5981B IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET Pin Description (continued) PIN NAME FUNCTION 11 2EC 2-Event Classification Detect or Wall Adapter Detect Output. A 1.5mA current sink is enabled at 2EC when a Type 2 PSE or a wall adapter is detected. When powered by a Type 2 PSE, the 2EC current sink is enabled after the isolation MOSFET is fully on until VIN drops below the UVLO threshold.
PAGE 9
IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET VDD VDD EN CLS CLASSIFICATION VDD 2EC D SET Q CLR Q D SET Q CLR Q 5V REGULATOR VDD 1.5mA 5V PG 46µA DET VON/VOFF VDD 230µA VDD THERMAL SHUTDOWN WAD R S Q 9V tDELAY ISWITCH VSS RTN ISOLATION SWITCH K x ISWITCH S I0 1/K I1 MUX MAX5981A MAX5981B SL 5V 2.
PAGE 10
MAX5981A/MAX5981B IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET Typical Operating Circuit 2-EVENT CLASSIFICATION DETECTION GND 2EC VDD RJ-45 AND BRIDGE RECTIFIER ENABLE 2EC/WAD DET MAX5981A MAX5981B 1.5mA DC-DC CONVERTER WAD CLS SMAJ58A 24V/48V BATTERY RCLS -54V GND PG RDET 24.
PAGE 11
IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET Operating Modes Depending on the input voltage (VIN = VDD - VSS), the MAX5981 operates in four different modes: PD detection, PD classification, mark event, and PD power. The devices enter PD detection mode when the input voltage is between 1.4V and 10.1V. The device enters PD classification mode when the input voltage is between 12.6V and 20V. The device enters PD power mode once the input voltage exceeds VON.
PAGE 12
MAX5981A/MAX5981B IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET Type 2 PSE detection flag. Alternatively, the 2EC output also serves as a wall adapter detection output when the MAX5981A/MAX5981B are powered by an external wall power adapter. See the Wall Power Adapter Detection and Operation section for more information. Power Mode (Wake Mode) The MAX5981A/MAX5981B enter power mode when VIN rises above the undervoltage lockout threshold (VON).
PAGE 13
IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET 3) Use short and wide traces for high-power paths. 4) Use the MAX5981A/MAX5981B evaluation kit layout as a reference. Operation with 12V Adapter Layout Procedure Careful PCB layout is critical to achieve high efficiency and low EMI.
PAGE 14
MAX5981A/MAX5981B IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET Typical Application Circuit ISOLATED 2-EVENT CLASSIFICATION OUTPUT GND GND 2EC VDD 2EC/WAD VAC DET 68nF MAX5981A MAX5981B CLS SMAJ58A VAC WAD 1.4mA 24/48V BATTERY 43.7I -54V WALK MODE INPUT PG PG 24.9kI VSS RTN WK SL RTN 1kI ISOLATED SLEEP MODE INPUT 60.4kI ULP -54V LED ISOLATED ULP MODE INPUT -54V -54V GND 33kI 1.37MI 249I 4.7µF 0.1µF 51.5kI ISOLATED +5.
PAGE 15
IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET PROCESS: BiCMOS For the latest package outline information and land patterns, (footprints) go to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
PAGE 16
MAX5981A/MAX5981B IEEE 802.3af/at-Compliant, Powered Device Interface Controllers with Integrated Power MOSFET Revision History REVISION NUMBER REVISION DATE 0 1/11 1 8/11 2 8/11 DESCRIPTION Initial release Revised General Description, Absolute Maximum Ratings, Electrical Characteristics, Pin Description, Typical Operating Circuit, LED Driver section, and Typical Application Circuit. Revised General Description, Electrical Characteristics, Typical Operating Characteristics, and Pin Description.