MAX5941A_06 Datasheet, PDF (1/24 Pages) Maxim Integrated Products – IEEE 802.3af-Compliant Power-Over-Ethernet Interface/PWM Controller for Power Devices

19-3069; Rev 4; 6/06
EVAALVUAAILTAIOBNLEKIT
IEEE 802.3af-Compliant Power-Over-Ethernet
Interface/PWM Controller for Power Devices
General Description
The MAX5941A/MAX5941B integrate a complete power
IC for powered devices (PD) in a power-over-ethernet
(PoE) system. The MAX5941A/MAX5941B provide a PD
interface and a compact DC-DC PWM controller suitable
for flyback and forward converters in either isolated or
nonisolated designs.
The MAX5941A/MAX5941B 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 MAX5941A/MAX5941B also integrate all the building
blocks necessary for implementing DC-DC fixed-
frequency isolated power supplies. These devices are 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 fre-
quency is internally trimmed to 275kHz ±10%, thus
reducing magnetics and filter components. The
MAX5941A allows an 85% operating duty cycle and can
be used to implement flyback converters. The MAX5941B
limits the operating duty cycle to less than 50% and can
be used in single-ended forward converters. The
MAX5941A/MAX5941B are designed to work with or with-
out an external diode bridge in front of the PD.
The MAX5941A/MAX5941B 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
Programmable Undervoltage Lockout
o PWM Controller
Wide Input Range: 18V to 67V
Current-Mode Control
Leading-Edge Blanking
Internally Trimmed 275kHz ±10% Oscillator
Soft-Start
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
MAX DUTY
CYCLE (%)
MAX5941AESE -40°C to +85°C 16 SO (S16M-6)
85
MAX5941ACSE 0°C to +70°C 16 SO (S16M-6)
85
MAX5941BESE -40°C to +85°C 16 SO (S16M-6)
50
MAX5941BCSE 0°C to +70°C 16 SO (S16M-6)
50
Pin Configuration
TOP VIEW
V+ ₁
V_DD 2
OPTO 3
SS_SHDN 4
ULVO 5
RCL 6
GATE 7
V_EE 8
MAX5941A
MAX5941B
SO
16 V_CC
15 NDRV
14 V-
13 CS
12 GND
11 PGOOD
10 PGOOD
9 OUT
________________________________________________________________ Maxim Integrated Products 1
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