Datasheet

SUPPLIER PHONE WEBSITE
AVX Corporation 843-946-0238 www.avxcorp.com
Bel Fuse Inc. 201-432-0463 www.belfuse.com
Coilcraft, Inc. 847-639-6400 www.coilcraft.com
Cooper Bussmann 916-941-1117 www.cooperet.com
Diodes Incorporated 805-446-4800 www.diodes.com
Fairchild Semiconductor 888-522-5372 www.fairchildsemi.com
Infineon Technologies AG 919-998-5334 www.infineon.com
IRC Inc. 361-992-7900 www.irctt.com
Murata Electronics North America, Inc. 770-436-1300 www.murata-northamerica.com
Panasonic Corp. 800-344-2112 www.panasonic.com
Pulse Engineering 858-674-8100 www.pulseeng.com
TDK Corp. 847-803-6100 www.component.tdk.com
Vishay 402-563-6866 www.vishay.com
_________________________________________________________________ Maxim Integrated Products 4
MAX5974C Evaluation Kit
Evaluates: MAX5974C
Component Suppliers
Quick Start
Required Equipment
• MAX5974CEVkit
• IEEE 802.3af/at-compliant PSE and Category 5e
Ethernet network cable
• -48V,1A-capableDCpowersupply
• Voltmeter
Hardware Connections
The EV kit is fully assembled and tested. Follow the steps
below to verify board operation. Caution: Do not turn on
the power supply until all connections are completed.
1) Use one of the following methods to power the EV kit:
• If network connectivity is required: Connect a
Category 5e Ethernet network cable from the EV
kit input port RJ45 MagJack connector (RJ45) to
the corresponding PSE Ethernet LAN connection,
which provides power to the EV kit. Ethernet jack J1
provides an interface with the Ethernet data signals
only.
• If network connectivity is not required: Connect
a -48V DC power supply between the VDD and
VSS PCB pads on the EV kit. Connect the power-
supply positive terminal to the VDD pad and the
negative terminal to the VSS PCB pad.
2) Activate the PSE power supply or turn on the external
DC power supply.
3) Using a voltmeter, verify that the EV kit provides +5V
across the +5V and PGND PCB pads. PGND is gal-
vanically isolated from the EV kit’s input VDD and
VSS PCB pads.
Detailed Description of Hardware
The MAX5974C EV kit is a fully assembled and tested
surface-mount circuit board that evaluates the MAX5974C
active-clamped, current-mode PWM controller. The EV kit
features a powered Ethernet port, a data-only Ethernet
port, and a MAX5969B IEEE 802.3af/at-compliant net-
work PD interface-controller IC.
The EV kit is a galvanically isolated 25W DC-DC con-
verter using the active-clamped, current-mode PWM
controller IC in a forward-feedback topology. The EV
kit receives power from an IEEE 802.3af/at-compliant
PSE and a UTP cable connected to the EV kit’s RJ45
MagJack. The EV kit uses a 1 x 1Gb RJ45 MagJack and
two diode-bridge power rectifiers (D1, D2) to separate
the -57V DC power sent by the PSE. The EV kit accepts
power from an endspan or midspan PSE network con-
figuration. The EV kit also provides Ethernet jack J1 for
interfacing to the Ethernet data signals. PCB pads VDD
and VSS are available for powering the EV kit, if network
connectivity is not required.
The EV kit output voltage is configured for +5V and
provides up to 4.7A output current. The EV kit circuit
achieves up to 93.5% efficiency using MOSFETs N1
and N2 for synchronous rectification on the secondary
side. Transformer T1 provides up to 1500V galvanic
isolation for the output. Isolated feedback voltage is
achieved using optical coupler U3 and voltage regulator
U4. Current-sense resistors R21 and R25 limit the peak
current through transistor N5 and primary transformer T1.
Capacitor C17 and transistor N4 form a clamping net-
work that protects transformer T1 against saturation due
to reverse current, by monitoring the voltage across the
IC’s CS input during auxiliary driver N4 off-time.
Note: Indicate that you are using the MAX5974C when contacting these component suppliers.