Datasheet

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MAX5986A–MAX5986C/MAX5987A

IEEE 802.3af-Compliant, High-Efficiency, Class 1/

Class 2, PDs with Integrated DC-DC Converter

19-6261; Rev 4; 12/14

Benefits and Features

S IEEE 802.3af Compliant

S PoE Class 1/Class 2 Classification

S Simplified Wall Adapter Interface

S Intelligent MPS

S Sleep and Ultra-Low-Power Mode (MAX5986A/

MAX5986B/MAX5986C)

S Efficient, Integrated DC-DC Converter (with

Integrated Switches)

S 8.7V to 60V Wide Input Voltage Range

S 3.0V to 14V Programmable Output Voltage Range

S Internal Compensation

S Fixed 215kHz/430kHz Switching Frequency

S Frequency Foldback for High-Efficiency Light-

Load Operation

S Built-In Output-Voltage Monitoring

S Open-Drain RESET Output (MAX5987A)

S Protects Against Overload, Output Short Circuit,

Output Overvoltage, and Overtemperature

S Hiccup-Mode Runaway Current Limit

S Back-Bias Capability to Optimize the Efficiency

S Integrated TVS Diode Withstands Cable Discharge

Event (CDE)

S Internal LDO Regulator with Up to 100mA Load

(MAX5987A)

S Fixed 3.3V or Adjustable Output Voltage Through

an External Resistive Divider

S 49mA (typ) Inrush Current Limit

S Pass 2kV, 200m CAT-6 Cable Discharge Event

General Description

The MAX5986A–MAX5986C/MAX5987A provide a

complete power-supply solution as IEEE

802.3af-com-

pliant Class 1/Class 2 Powered Devices (PDs) in a Power-

over-Ethernet (PoE) system. The devices integrate the PD

interface with an efficient DC-DC converter, offering a low

external part count PD solution. The MAX5987A includes

a low-dropout regulator and the MAX5986A–MAX5986C

include sleep and ultra-low power modes.

The PD interface provides a detection signature and

a Class 1/Class 2 classification signature with a single

external resistor. The PD interface also provides an

isolation power MOSFET, a 60mA (max) inrush current

limit, and a 323mA operating current limit.

The integrated step-down DC-DC converter uses a peak

current-mode control scheme and provides an easy-to-

implement architecture with a fast transient response.

The step-down converter operates in a wide input volt-

age range from 8.7V to 60V and supports up to 6.49W

of input power. The MAX5986A/MAX5986B/MAX5987A

operate at a fixed 215kHz switching frequency and

the MAX5986C operates at a fixed 430kHz switching

frequency. The DC-DC converter operates at a fixed

switching frequency, with an efficiency-boosting

frequency foldback that reduces the switching frequency

by half at light loads.

The devices feature an input undervoltage-lockout

(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 devices also feature overtemperature

shutdown, short-circuit protection, output overvoltage

protection, and hiccup current limit for enhanced perfor-

mance and reliability.

The MAX5986A–MAX5986C/MAX5987A are available

in a 16-pin, 5mm x 5mm, TQFN power package and

operate over the -40°C to +85°C temperature range.

IEEE is a registered service mark of the Institute of Electrical

and Electronics Engineers, Inc.

WiMAX is a registered certification mark and registered service

mark of WiMAX Forum.

Ordering Information appears at end of data sheet.

For related parts and recommended products to use with this part,

refer to www.maximintegrated.com/MAX5986A/MAX5987A.related.

Applications

IEEE 802.3af-Powered Devices

IP Phones

Wireless Access Nodes

IP Security Cameras

WiMAX

Base Stations

EVALUATIO N KIT AVAILABLE

For pricing, delivery, and ordering information, please contact Maxim Direct at

1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

Summary of content (23 pages)

PAGE 1
EVALUATIONKITAVAILABLE MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter General Description The MAX5986A–MAX5986C/MAX5987A provide a complete power-supply solution as IEEE® 802.3af-compliant Class 1/Class 2 Powered Devices (PDs) in a Powerover-Ethernet (PoE) system. The devices integrate the PD interface with an efficient DC-DC converter, offering a low external part count PD solution.
PAGE 2
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND, unless otherwise noted.) VDD to GND............................................................-0.3V to +70V (100V, 100ms, RTEST = 3.3kω) (Note 1) VCC, WAD, RREF to GND......................... -0.3V to (VDD + 0.3V) AUX, LDO_IN, LED to GND..................................... -0.3V to 16V LDO_OUT to GND............................
PAGE 3
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter ELECTRICAL CHARACTERISTICS (continued) (VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND, C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected. VCLASS2 = 0V, VMPS = 0V. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted.
PAGE 4
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter ELECTRICAL CHARACTERISTICS (continued) (VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND, C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 5
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter ELECTRICAL CHARACTERISTICS (continued) (VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND, C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 6
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter ELECTRICAL CHARACTERISTICS (continued) (VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND, C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 7
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter ELECTRICAL CHARACTERISTICS (continued) (VDD = 48V, RSIG = 24.9kω, LED, VCC, SL, ULP, WK, RESET, LDO_OUT unconnected, WAD = LDO_EN = LDO_IN = PGND = GND, C1 = 68nF, C2 = 10µF, C3 = 1µF (see Figure 3), VFB = VAUX = 0V, LX unconnected. All voltages are referenced to GND, unless otherwise noted. TA = TJ = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 8
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter IIN RTEST dRi = 1V (VINi + 1 - VINi) = (IINi + 1 - IINi) (IINi + 1 - IINi) IOFFSET = IINi - MAX5986A 1ms/10ms/100ms dRi IINi + 1 EVALUATION BOARD 100V VINi dRi IINi IOFFSET VINi Figure 1. MAX5986A/MAX5987A Internal TVS Test Setup 1V VINi + 1 VIN Figure 2.
PAGE 9
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) CLASSIFICATION CURRENT vs. INPUT VOLTAGE CLASSIFICATION SETTLING TIME 10.58 CLASSIFICATION CURRENT (mA) MAX5986A toc06 MAX5986A toc05 10.60 10.56 VDD 10V/div GND 10.54 10.52 10.50 10.48 10.46 IDD 10mA/div 0mA 10.44 10.42 10.40 14.1 12.6 15.6 17.1 18.6 20.
PAGE 10
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Typical Operating Characteristics (continued) (TA = +25°C, unless otherwise noted.) VIN = 36V 95 VIN = 48V 90 85 VIN = 57V 80 VIN = 12V 95 EFFICIENCY (%) 90 EFFICIENCY (%) 100 MAX5986A toc11 100 75 85 80 75 70 70 65 65 VIN = 36V VIN = 48V VIN = 57V 60 60 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 0.
PAGE 11
MAX5986A–MAX5986C/MAX5987A IEEE 802.
PAGE 12
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Pin Description (continued) PIN MAX5986A/MAX5986B/ MAX5986C MAX5987A 6 6 NAME FUNCTION GND Ground. Reference rail for the device. It is also the “quiet” ground for all voltage reference (e.g., FB is referenced to this GND). 7 7 VDRV Internal 5V Regulator Voltage Output. The internal voltage regulator provides 5V to the MOSFET driver and other internal circuits.
PAGE 13
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Detailed Description PD Interface The devices include complete interface functions for a PD to comply with the IEEE 802.3af standard as a Class 1/Class 2 PD. The devices provide the detection and classification signatures using a single external signature resistor. An integrated MOSFET provides isolation from the buck converter when the PSE has not applied power.
PAGE 14
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Sleep and Ultra-Low Power Modes (MAX5986A–MAX5986C) The MAX5986A–MAX5986C feature a sleep mode and an ultra-low power mode in which the internal p-channel isolation MOSFET is kept on and the buck regulator is off. In sleep mode, the LED driver output (LED) pulse width of the MAX5986B/MAX5986C modulates the LED current with a 25% duty cycle, while the MAX5986A does 100% only.
PAGE 15
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Frequency Foldback Protection for High-Efficiency Light-Load Operation The devices enter frequency foldback mode when eight consecutive inductor current zero-crossings occur. The switching frequency is 215kHz or 430kHz under loads large enough that the inductor current does not cross zero. In frequency foldback mode, the switching frequency is reduced to 107.
PAGE 16
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Inductor Selection Choose an inductor with the following equation: where LIR is the ratio of the inductor ripple current to full load current at the minimum duty cycle. Choose LIR between 20% to 40% for best performance and stability. Use an inductor with the lowest possible DC resistance that fits in the allotted dimensions.
PAGE 17
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Table 1. Design Selection Table OUTPUT CIN COUT L CLASS 33FH/1.4A 1 3x22FF/6.3V 47FH/1.6A 1 or 2 2x10FF/16V 220F/0.8A* 1 or 2 CERAMIC ELECTROLYTIC CERAMIC 2.2FF/100V 10FF/63V 3x22FF/6.3V 5V 2.2FF/100V 10FF/63V 12V 2.2FF/100V 10FF/63V 3.3V *100μH/0.8A is recommendedfor with the MAX5986C.
PAGE 18
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Typical Application Circuits RJ-45 AND BRIDGE RECTIFIER C1 68nF 1µF C2 10µF VDD VCC WAD AUX C3 1µF VDRV L0 47µH CLASS2 MPS LX WK TO µP OPEN-DRAIN OUTPUTS OR PULLDOWN SWITCHES R1 75kI MAX5986A ULP 5V OUTPUT C4 47µF FB SL R2 24.9kI RSL 60.4kI LED RREF RSIG 24.9kI GND PGND 0I Figure 3.
PAGE 19
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Typical Application Circuits (continued) RJ-45 AND BRIDGE RECTIFIER C1 68nF 1µF C2 10µF VDD VCC WAD AUX VDRV C3 1µF L0 220µH* CLASS2 LX MPS WK TO µP OPEN-DRAIN OUTPUTS OR PULLDOWN SWITCHES R1 215kI MAX5986B MAX5986C ULP 12V OUTPUT C4 10µF FB SL R2 24.9kI RSL 60.4kI LED RREF RSIG 24.9kI GND PGND 0I *USE 110µH FOR MAX5986C Figure 4.
PAGE 20
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Typical Application Circuits (continued) RJ-45 AND BRIDGE RECTIFIER C1 68nF 1µF LDO_FB C2 10µF VDD VCC WAD AUX VDRV C3 1µF L0 47µH CLASS2 LX 5V OUTPUT MPS C5 1µF R1 75kI MAX5987A LDO_IN TO 5V OUTPUT LDO_OUT C4 47µF FB C6 1µF R2 24.9kI LED RREF RSIG 24.9kI GND PGND 0I Figure 5. MAX5987A 5V Buck Regulator Output and 3.
PAGE 21
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Functional Diagram MAX5986A MAX5986B MAX5986C MAX5987A VDD VCC 5V TVS HOT-SWAP CONTROLLER DETECTION CLASSIFICATION GND 5V RREF WAD PD VOLTAGE MONITOR AUX 5V 5V 1.
PAGE 22
MAX5986A–MAX5986C/MAX5987A IEEE 802.3af-Compliant, High-Efficiency, Class 1/ Class 2, PDs with Integrated DC-DC Converter Package Information Chip Information PROCESS: BiCMOS For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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.
PAGE 23
MAX5986A–MAX5986C/MAX5987A IEEE 802.