MAX5942B

Features:

 Powered Device Interface
    Fully Integrated IEEE 802.3af-Compliant PD Interface
    PD Detection and Programmable Classification Signatures
    Less than 10A 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/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


Application

IP Phones
Wireless Access Nodes
Internet Appliances
Computer Telephony
Security Cameras
Power Devices in Power-Over-Ethernet/Power-Over-MDI


Pinout




Specifications

GND....................................................................-0.3V to +80V
OUT, PGOOD ..........................................-0.3V to (GND + 0.3V)
RCL, GATE .........................................................-0.3V to +12V
UVLO....................................................................-0.3V to +8V
PGOOD to OUT........................................-0.3V to (GND + 0.3V)
V+ to V-..............................................................-0.3V to +80V
VDD to V-............................................................-0.3V to +40V
VCC to V-.........................................................-0.3V to +12.5V
FB, NDRV, SS_SHDN, CS to V- ..................-0.3V to (VCC + 0.3V)
Maximum Input/Output Current (continuous)
                              OUT to V_EE ........................................500mA
                              GND, RCL to V_'''''''.................................70mA
UVLO, PGOOD, PGOOD to V_EE ...........................................20mA
GATE to V_EE........................................................................80mA
VDD, VCC...........................................................................20mA
NDRV Continuous ..............................................................25mA
NDRV (pulsed for less than 1s) ..........................................±1A
Continuous Power Dissipation (TA = +70°C)
16-Pin SO (derate 9.1mW/°C above +70°C)................727mW
Operating Temperature Ranges
MAX5942_CSE...................................................0°C to +70°C
MAX5942_ESE................................................-40°C to +85°C
Storage Temperature Range .......................-65°C to +150°C
Junction Temperature...................................................+150°C
Lead Temperature (soldering, 10s) .............................+300°C

Description

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 powergood status outputs.

The MAX5942A/MAX5942B also integrate all the building blocks necessary for implementing DC-DC fixedfrequency 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 MAX59412A 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.