MAX5942A Datasheet, PDF (1/24 Pages) Maxim Integrated Products – IEEE 802.3af Power-Over-Ethernet Interface/PWM Controller for Power Devices

19-3024; Rev 0; 10/03
IEEE 802.3af Power-Over-Ethernet
Interface/PWM Controller for Power Devices
General 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 detec-
tion signature, a classification signature, and an integrat-
ed isolation switch with programmable inrush current
control. These devices also feature power-mode under-
voltage lockout (UVLO) with wide hysteresis and power-
good status outputs.
The MAX5942A/MAX5942B also integrate all the build-
ing 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
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 with-
out an external diode bridge in front of the PD.
The MAX5942A/MAX5942B are available in 16-pin SO
packages.
Applications
IP Phones
Wireless Access Nodes
Internet Appliances
Computer Telephony
Security Cameras
Power Devices in Power-Over-Ethernet/
Power-Over-MDI
Typical Operating Circuit appears at end of data sheet.
Features
o 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/PGOOD Outputs Enable PWM
Controller
o 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
Ordering Information
PART
TEMP RANGE ^PIN-
MAX DUTY
PACKAGE CYCLE (%)
MAX5942AESE* -40°C to +85°C 16 SO
85
MAX5942ACSE 0°C to +70°C 16 SO
85
MAX5942BESE* -40°C to +85°C 16 SO
50
MAX5942BCSE 0°C to +70°C 16 SO
50
*Future product—contact factory for availability.
Pin Configuration
TOP VIEW
V+ ₁
V_DD 2
FB 3
SS_SHDN 4
ULVO 5
RCL 6
GATE 7
V_EE 8
MAX5942A
MAX5942B
SO
16 V_CC
15 NDRV
14 V-
13 CS
12 GND
11 PGOOD
10 PGOOD
9 OUT
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