MAX5969B Evaluation Kit
Evaluates: MAX5969A/MAX5969B
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Quick Start
Required Equipment
• IEEE 802.3af/at-compliant PSE and Category 5e
Ethernet network cable
• -48V,1A-capableDCpowersupply
• MAX5969BEVkit
• Voltmeter
Hardware Connections
The MAX5969B EV kit is fully assembled and test-
ed. 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 connector to the corre-
sponding PSE Ethernet LAN connection, which
provides power to the EV kit. A modular RJ45 jack
(J3) provides an interface with the Ethernet data
signals only.
• Ifnetworkconnectivityisnotrequired: Connect
a -48V DC power supply between the VDD and
VSS pads on the EV kit. Connect the power-supply
positive terminal to the VDD pad and the negative
terminal to the VSS 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 +12V
across the +12V and GND pads. GND is galvanically
isolated from the EV kit’s input VDD and WAD pads.
Detailed Description of Hardware
The MAX5969B EV kit features an Ethernet port,
network PD interface-controller circuit for -57V
supply rail systems. The EV kit contains a MAX5969B
IEEE 802.3af/at-compliant PD controller IC in a 10-pin
TDFN package with an exposed pad. The IC is used in
PoE applications for powering PDs from an unshielded
twisted-pair (UTP) Ethernet Category 5e network cable
and PSE port using endspan or midspan Ethernet sys-
tems.
The EV kit receives power from an IEEE 802.3af/at-
compliant PSE and a UTP cable connected to the EV
kit’s RJ45 magnetic jack. The EV kit uses a 1 x 1GbE
RJ45 magnetic jack and two diode-bridge power recti-
fiers (D3, D4) to separate the -57V DC power sent by
the PSE. The EV kit accepts power from an endspan
or midspan PSE network configuration. The EV kit also
provides an RJ45 jack (J3) for interface to the Ethernet
data signals only.
The EV kit can also accept power from a wall adapter
power source. When a wall adapter power source is
detected between the WAD and RTN PCB pads, the IC’s
internal isolation switch disconnects VSS from RTN, which
allows the wall adapter to supply power to the EV kit.
The EV kit demonstrates the full functionality of the
MAX5969B, such as PD detection signature, PD
classification signature, in-rush current control, and
UVLO. The EV kit also provides modular jack J3 to inter-
face with the Ethernet data signals from the RJ45 mag-
netic jack. Resistor R1 sets the PD detection signature;
the PD classification signature is determined by resistor
R2.
The EV kit’s galvanically isolated 22.7W flyback DC-DC
converter uses a MAX15000A current-mode PWM
controller. The MAX5969B’s VDD and RTN pins pro-
vide power for the DC-DC converter input circuit. The
DC-DC converter is configured for an output voltage of
+12V and provides up to 1.9A at the output, while
achieving up to 89% efficiency. Minimal component
count is achieved using a single transistor (N1) flyback
DC-DC converter topology. The surface-mount trans-
former (T1) provides up to 1500V galvanic isolation for
the output. Current-sense resistors R12 and R13 limit
the peak current through transistor N1 and the primary
of transformer T1. Isolated feedback voltage is achieved
using optical coupler U3 and shunt regulator U4. Voltage
feedback resistors R23 and R25 set the output voltage.
Resistor R26 and capacitor C21 form a snubber network
that suppresses transient overvoltage ringing at diode
D7 caused by transformer T1’s leakage inductance and
the junction capacitance of diode D7.
Internal UVLO, soft-start, and thermal shutdown within
the MAX15000A provide for a robust 22.7W isolated
power-supply design. The MAX15000A PWM controller
operates at 600kHz and the switching duty cycle is lim-
ited to 50% (max). Refer to the MAX15000 IC data sheet
for more information on this controller.
Warning: The MAX5969B 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
when working with high-voltage electrical equipment.