MAX5988B
IEEE 802.3af-Compliant, High-Efficiency, Class 1/Class 2 Powered Devices with Integrated DC-DC Converters
Reduce BOM Costs with Highly Integrated Powered Devices for PoE Applications
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Key Features
Applications/Uses
| Compliance | IEEE 802.3af IEEE 802.3at |
| RDS(ON) (Ω) (PD MOSFET) | 1.2 |
| PWM | No |
| UVLO Threshold (V) | 38.6 |
| Package/Pins | TQFN/20 |
| Oper. Temp. (°C) | -40 to +85 |
| Budgetary Price (See Notes) | 4.18 |
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Parameters
| Compliance | IEEE 802.3af IEEE 802.3at |
| RDS(ON) (Ω) (PD MOSFET) | 1.2 |
| PWM | No |
| UVLO Threshold (V) | 38.6 |
| Package/Pins | TQFN/20 |
| Oper. Temp. (°C) | -40 to +85 |
| Budgetary Price (See Notes) | 4.18 |
Key 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 (Active-Low 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)
Applications/Uses
- IEEE® 802.3af-Powered Devices
- IP Phones
- IP Security Cameras
- WiMAX® Base Stations
- Wireless Access Nodes
Description
The MAX5988A/MAX5988B provide a complete power-supply 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-to-implement 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 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 performance and reliability.
All devices are available in a 20-pin, 4mm × 4mm, TQFN power package and operate over the -40°C to +85°C temperature range.
Technical Docs
Support & Training
Search our knowledge base for answers to your technical questions.
Filtered SearchOur dedicated team of Applications Engineers are also available to answer your technical questions. Visit our support portal .
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