MAX5969B Evaluation Kit

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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.