Document
MAX5988A/MAX5988B
EVALUATION KIT AVAILABLE
IEEE 802.3af-Compliant, High-Efficiency, Class 1/Class 2, Powered Devices with Integrated DC-DC Converter
General Description
The MAX5988A/MAX5988B provide a complete powersupply solution as IEEE® 802.3af-compliant 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 devices also include a low-dropout regulator, MPS, 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 321mA (typ) operating current limit.
The integrated step-down DC-DC converter uses a peak current-mode control scheme and provides an easy-toimplement architecture with a fast transient response. The step-down converter operates in a wide input voltage range from 8.8V to 60V and supports up to 6.49W of input power at 1.3A load. The DC-DC converter operates at a fixed 215kHz switching frequency, with an efficiencyboosting 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 performance and reliability.
All devices are available in a 20-pin, 4mm x 4mm, TQFN power package and operate over the -40°C to +85°C temperature range.
Applications
●● IEEE 802.3af-Powered Devices
●● IP Phones
●● Wireless Access Nodes
●● IP Security Cameras ●● WiMAX® Base Stations
Benefits and Features
●● High Integration Saves Space and BOM Cost • Efficient, Integrated DC-DC Converter (with Integrated Switches) • Built-In Output-Voltage Monitoring • Protects Against Overload, Output Short Circuit, Output Overvoltage, and Overtemperature • Integrated TVS Diode Withstands Cable Discharge Event (CDE) • Internal LDO Regulator with Up to 100mA Load
●● Application-Specific Features Speed Design • IEEE 802.3af Compliant • PoE Class 1/Class 2 Classification Set with Single Resistor • Intelligent Maintain Power Signature (MPS) • Simplified Wall Adapter Interface • Pass 2kV, 200m CAT-6 Cable Discharge Event
●● High Efficiency During Light Loads Reduces Power Consumption • Sleep and Ultra-Low-Power Mode • Frequency Foldback for High-Efficiency Light-Load Operation • Back-Bias Capability to Optimize the Efficiency
●● Robust Performance • 8.8V to 60V Wide Input Voltage Range • Hiccup-Mode Runaway Current Limit • 49mA (typ) Inrush Current Limit • Open-Drain RESET Output
●● Easy to Design With • 3.0V to 14V Programmable Output Voltage Range • Internal Compensation • Fixed 215kHz Switching Frequency • Fixed 3.3V or Adjustable Output Voltage through an External Resistive Divider (LDO)
Ordering Information/Selector Guide appears at end of data sheet.
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.
19-6476; Rev 3; 1/15
MAX5988A/MAX5988B
IEEE 802.3af-Compliant, High-Efficiency, Class 1/Class 2, Powered Devices with Integrated DC-DC Converter
Absolute Maximum Ratings
(All voltages referenced to GND, unless otherwise noted.) VDD to GND...........................-0.3V to +70V (internally clamped)
(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............................... -0.3V to (LDO_IN + 0.3V) LDO_FB to GND.......................................................-0.3V to +6V LX to GND................................................. -0.3V to (VCC + 0.3V) LDO_OUT, VDRV, FB, RESET, WK, SL, ULP, MPS, CLASS2
to GND...............................................................-0.3V to +6V
VDRV to VDD............................................. -0.3V to (VDD + 0.3V) PGND to GND.......................................................-0.3V to +0.3V LX Total RMS Current............................................................1.6A
Continuous Power Dissipation (TA = + 70NC) TQFN (derate 28.6mW/NC above +70NC)...............2285.7mW
Operating Temperature Range........................... -40NC to +85NC Junction Temperature......................................................+150NC Storage Temperature Range............................. -65NC to +150NC Lead Temperature (soldering, 10s).................................+300NC Sold.