The MAX5941B evaluation kit (EV kit) is a fully assembled
and tested surface-mount circuit board featuring an
Ethernet port, network powered device (PD) interface
and DC-DC PWM controller circuit for -48V systems. The
MAX5941B is used in power-over-LAN applications
requiring a DC-DC, fixed-frequency, isolated power supply
from an Ethernet network port for PDs such as IP
phones, wireless access nodes, and security cameras.
The MAX5941B EV kit receives power from IEEE®
802.3af-compliant power sourcing equipment (PSE).
Refer to the MAX5922 and MAX5935 data sheets for
PSE controllers. The PSE provides the required -44V to
-57V DC power over an unshielded, twisted-pair
Ethernet network cable to the EV kit. The EV kit features
a 10/100BASE-TX voice-over-IP (VoIP) magnetic module
and separate diode bridges for separating the DC
power from the module provided by an endspan/endpoint
or midspan Ethernet system.
The MAX5941B EV kit demonstrates the PD interface and
DC-DC PWM features. The EV kit also demonstrates the
full functionality of the MAX5941B. Features such as PD
detection signature, configurable PD classification signature,
programmable inrush current, and programmable
undervoltage lockout (UVLO) can be evaluated. All of
these features are configurable on the EV kit.
The MAX5941B EV kit also features a galvanically isolated,
13.2W, 275kHz switching frequency DC-DC converter,
which uses the MAX5941B current-mode PWM controller
section of the IC. Power for the forward DC-DC
converter circuit is provided from the MAX5941B's -48V
output, or from a local input DC supply, such as a wall
cube. The DC-DC converter is configured for an output
voltage of +3.3V and provides up to 4A. High efficiency
(up to 85%) is achieved using a single transistor, forward
DC-DC converter topology on the primary side, and synchronous
rectifiers on the secondary side. The surface-mount
transformer provides up to 1500VRMS galvanic isolation
for the output. UVLO, soft-start, and current limit
provide a robust 13.2W isolated power supply.
Warning: The MAX5941B EV kit is designed to operate
with high voltages. Dangerous voltages are present in this
EV kit and in equipment connected to it. Users who power
up this EV kit, or power the sources connected to it, must
follow safety procedures appropriate for working with
high-voltage electrical equipment.
Under severe fault or failure conditions, this EV kit may
dissipate large amounts of power, which could result in
the mechanical ejection of a component or of component
debris at high velocity. Operate this kit with care to avoid
possible personal injury.
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