MAX5953A Datasheet, PDF (1/27 Pages) Maxim Integrated Products – IEEE 802.3af PD Interface and PWM Controllers with Integrated Power MOSFETs

19-3945; Rev 1; 7/06
IEEE 802.3af PD Interface and PWM Controllers
with Integrated Power MOSFETs
General Description
The MAX5953A/MAX5953B/MAX5953C/MAX5953D
integrate a complete power IC solution for Powered
Devices (PD) in a Power-Over-Ethernet (PoE) system, in
compliance with the IEEE 802.3af standard. The
MAX5953A/MAX5953B/MAX5953C/MAX5953D provide
the PD with a detection signature, a classification sig-
nature, and an integrated isolation switch with program-
mable inrush current control. These devices also
integrate a voltage-mode PWM controller with two
power MOSFETs connected in a two-switch voltage-
clamped DC-DC converter configuration.
An integrated MOSFET provides PD isolation during
detection and classification. All devices guarantee a
leakage current offset of less than 10µA during the
detection phase. A programmable current limit pre-
vents high inrush current during power-on. The devices
feature power-mode undervoltage lockout (UVLO) with
wide hysteresis and long deglitch time to compensate
for twisted-pair-cable resistive drop and to assure
glitch-free transition between detection, classification,
and power-on/-off phases. The MAX5953A/MAX5953C
have an adjustable UVLO threshold with the default
value compliant to the 802.3af standard, while the
MAX5953B/MAX5953D have a lower and fixed UVLO
threshold compatible with some legacy pre-802.3af
power-sourcing equipment (PSE) devices.
The DC-DC converters are operable in either forward or
flyback configurations with a wide input voltage range
from 11V to 76V and up to 15W of output power. The
voltage-clamped power topology enables full recovery
of stored magnetizing and leakage inductive energy for
enhanced efficiency and reliability. When using the
high-side MOSFET, the controller can be configured as
a buck converter. A look-ahead signal for driving sec-
ondary-side synchronous rectifiers can be used to
increase efficiency. A wide array of protection features
include UVLO, over-temperature shutdown, and short-
circuit protection with hiccup current limit for enhanced
performance and reliability. Operation up to 500kHz
allows for smaller external magnetics and capacitors.
The MAX5953A/MAX5953B/MAX5953C/MAX5953D are
available in a high-power (2.22W), 7mm x 7mm ther-
mally enhanced thin QFN package.
Applications
IEEE 802.3af Powered
Devices
IP Phones
Wireless Access Nodes
Internet Appliances
Security Cameras
Computer Telephony
Features
♦ 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 MOSFET
Programmable Inrush Current Control
Programmable Undervoltage Lockout
(MAX5953A/MAX5953C)
♦ DC-DC Converter
Clamped, Two-Switch Power IC for High
Efficiency
Integrated High-Voltage 0.4Ω Power MOSFETs
Up to 15W Output Power
Bias Voltage Regulator with Automatic High-
Voltage Supply Turn-Off
11V to 76V Wide Input Voltage Range
Feed-Forward Voltage-Mode Control for Fast
Input Transient Rejection
Programmable Undervoltage Lockout
Overtemperature Shutdown
Indefinite Short-Circuit Protection with
Programmable Fault Integration
Integrated Look-Ahead Signal for Secondary-
Side Synchronous Rectification
> 90% Efficiency with Synchronous
Rectification
Up to 500kHz Switching Frequency
♦ High-Power (2.22W), 7mm x 7mm Thermally
Enhanced Lead-Free Thin QFN Package
Ordering Information
PART
PIN-PACKAGE
PKG CODE
MAX5953AUTM+
48 TQFN
T4877-6
MAX5953BUTM+
48 TQFN
T4877-6
MAX5953CUTM+
48 TQFN
T4877-6
MAX5953DUTM+
48 TQFN
T4877-6
Operating junction temperature range is 0°C to +125°C.
+Denotes lead-free package.
Pin Configuration and Typical Operating Circuit appear at
end of data sheet.
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