MAX5942B IEEE 802.3af Power-Over-Ethernet Interface/PWM Controller for Power Devices
Product Details
The MAX5942A/MAX5942B integrate a complete power IC for powered devices (PD) in a power-over-ethernet (PoE) system. The MAX5942A/MAX5942B provide a PD interface and a compact DC-DC PWM controller suitable for flyback and forward converters in either isolated or nonisolated designs.
The MAX5942A/MAX5942B PD interface complies with the IEEE™ 802.3af standard, providing the PD with a detection signature, a classification signature, and an integrated isolation switch with programmable inrush current control. These devices also feature power-mode undervoltage lockout (UVLO) with wide hysteresis and power-good status outputs.
The MAX5942A/MAX5942B also integrate all the building blocks necessary for implementing DC-DC fixed-frequency isolated power supplies. This device is a current-mode controller with an integrated high startup circuit suitable for isolated telecom/industrial voltage range power supplies. A high-voltage startup circuit allows the PWM controller to draw power directly from the 18V to 67V input supply during startup. The switching frequency is internally trimmed to 275kHz ±10%, thus reducing magnetics and filter components. The MAX5942A allows an 85% operating duty cycle and can be used to implement flyback converters. The MAX5942B limits the operating duty cycle to less than 50% and can be used in single-ended forward converters. The MAX5942A/MAX5942B are designed to work with or without an external diode bridge in front of the PD.
The MAX5942A/MAX5942B are available in 16-pin SO packages.
Applications
- Computer Telephony
- Internet Appliances
- IP Phones
- Power Devices in Power-Over-Ethernet/Power-Over-MDI
- Security Cameras
- Wireless Access Nodes
Features and Benefits
- Powered Device Interface
- Fully Integrated IEEE 802.3af-Compliant PD Interface
- PD Detection and Programmable Classification Signatures
- Less than 10µA Leakage Current Offset During Detection
- Integrated MOSFET for Isolation and Inrush Current Limiting
- Gate Output Allows External Control of the Internal Isolation FET
- Programmable Inrush Current Control/ULVO
- PGOOD/Active-Low PGOOD Outputs Enable PWM Controller
- PWM Controller
- Wide Input Range: 18V to 67V
- Isolated (Without Optocoupler) or Nonisolated Power Supply
- Current-Mode Control
- Leading-Edge Blanking
- Internally Trimmed 275kHz ±10% Oscillator
- Soft-Start