MAX5940A Datasheet, PDF (1/15 Pages) Maxim Integrated Products – IEEE 802.3af PD Interface Controller For Power-Over-Ethernet

19-2991; Rev 0; 10/03
IEEE 802.3af PD Interface Controller
For Power-Over-Ethernet
General Description
The MAX5940A/MAX5940B provide complete interface
function for a powered device (PD) to comply with the
IEEE 802.3af standard in a power-over-ethernet system.
MAX5940A/MAX5940B provide the PD with a detection
signature, a classification signature, and an integrated
isolation switch with programmable inrush current con-
trol. These devices also feature power-mode undervolt-
age lockout (UVLO) with wide hysteresis, and
power-good outputs.
An integrated MOSFET provides PD isolation during
detection and classification. The MAX5940A/MAX5940B
guarantee a leakage current offset of less than 10µA dur-
ing the detection phase. A programmable current limit
prevents high inrush current during power-on. The device
features power-mode 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 MAX5940A provides an active-high (PGOOD) open-
drain output and a fixed UVLO threshold. The MAX5940B
provides both active-high (PGOOD) and active-low
(PGOOD) outputs and has an adjustable UVLO threshold
with the default value compliant to the 802.3af standard.
The MAX5940A/MAX5940B are designed to work with or
without an external diode bridge.
The MAX5940A/MAX5940B are available in 8-pin SO
packages and are rated over the extended temperature
range of -40°C to +85°C.
IP Phones
Applications
Security Cameras
Wireless Access Nodes IEEE 802.3af Power Devices
Computer Telephony
Features
o Fully Integrated IEEE 802.3af-Compliant PD
Interface
o PD Detection and Programmable Classification
Signatures
o Less than 10µA Leakage Current Offset During
Detection
o Integrated MOSFET For Isolation and Inrush
Current Limiting
o Gate Output Allows External Control of the
Internal Isolation MOSFET
o Programmable Inrush Current Control
o Programmable Undervoltage Lockout
(MAX5940B Only)
o Wide UVLO Hysteresis Accommodates Twisted-
Pair Cable Voltage Drop
o PGOOD/PGOOD Outputs to Enable Downstream
DC-DC Converters
o -40°C to +85°C Operating Temperature Range
Ordering Information
PART
MAX5940AESA
MAX5940BESA
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-
PACKAGE
8 SO
8 SO
UVLO
Fixed
Adjustable
Pin Configurations appear at end of data sheet.
Typical Operating Circuits
D1*
GND
60V
D2*
-48V
*OPTIONAL.
68nF
R_DISC
25.5kΩ
R_CL
2
RCLASS
8
GND
MAX5940A
3
6
GATE
PGOOD
4
V_EE
5
OUT
DC-DC CONVERTER
V+
C_OUT
MAX5014
GND
SS_SHDN
C_GATE
V_REG
LOAD
Typical Operating Circuits continued at end of data sheet.
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