Datasheet

General Description
The MAX5974C evaluation kit (EV kit) is a fully assembled
and tested surface-mount circuit board featuring the
MAX5974C active-clamped, spread-spectrum, current-
mode PWM controller for Power-over-Ethernet (PoE)
powered device (PD) applications. The EV kit is a
compact and low-cost design used in power-over-
LAN (PoLAN) applications requiring DC power from an
Ethernet network port for PDs such as IP phones, wire-
less access nodes, and security cameras.
The EV kit features a galvanically isolated 25W, 250kHz
switching-frequency, active-clamped, synchronous-rec-
tified forward DC-DC converter using the IC. The device
circuit achieves high efficiency up to 93.5% using a
forward DC-DC converter topology. The surface-mount
transformer provides up to +1500V galvanic isolation for
the output. The EV kit output voltage is configured for
+5V and provides up to 4.7A load current.
The EV kit includes the MAX5969B IEEE
M
802.3af/at-
compliant network PD interface controller IC, which pro-
vides PD detection signature, PD classification signature,
inrush current control, and undervoltage lockout (UVLO).
The EV kit circuit receives its power from IEEE 802.3af/
at-compliant power-sourcing equipment (PSE). The PSE
provides the required -39V to -57V DC power over an
unshielded twisted-pair Ethernet network cable to the
EV kit’s RJ45 MagJack
M
. The EV kit features a 1 x 1Gb
RJ45 MagJack and two full-bridge diodes for separat-
ing the DC power provided by an endspan or midspan
Ethernet system.
The EV kit circuit can also be powered by a +37V to
+57V wall adapter power source, applied at the PWR+
and PWR- PCB pads. When a wall adapter power source
is detected, it always takes precedence over the PSE
source, allowing the wall adapter to power the EV kit.
Warning: The EV kit is designed to operate with high
voltages. Dangerous voltages are present on this EV kit
and on equipment connected to it. Users who power up
this EV kit or power the sources connected to it must be
careful to follow safety procedures appropriately to work
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.
Features
S IEEE 802.3af/at-Compliant PD Interface Circuit
S -39V to -57V Startup Input Voltage Range
S Demonstrates an Isolated 25W Active-Clamped,
Synchronous-Rectified Forward DC-DC Converter
S Demonstrates Up to 93.5% Efficiency
S Isolated +5V Output at 4.7A
S PD Detection and Configurable Classification
Signatures
S Inrush Current Limit of 180mA (max)
S 2-Event Classification or Wall Adapter Detect
Output
S Internal UVLO at +38V
S Evaluates Endspan and Midspan Ethernet
Systems
S Simplified Wall Adapter Interface
S Proven PCB Layout
S Fully Assembled and Tested
EFFICIENCY vs. OUTPUT CURRENT
OUTPUT CURRENT(A)
EFFICIENCY (%)
4321
10
20
30
40
50
60
70
80
90
100
0
05
V
IN
= 48V
V
IN
= 57V
V
IN
= 42V
MAX5974C Evaluation Kit
Evaluates: MAX5974C
_________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
19-5262; Rev 0; 11/11
Ordering Information appears at end of data sheet.
IEEE is a registered service mark of the Institute of Electrical
and Electronics Engineers, Inc.
MagJack is a registered trademark of Bel Fuse Inc.
Figure 1. MAX5974C EV Kit Efficiency vs. Output Current at
V
IN
= 42V, 48V, and 57V