Datasheet

MAX5980 Evaluation Kit
Evaluates: MAX5980
11Maxim Integrated
The EV kit PSE circuit requires a -32 to -60V power sup-
ply (-48V/-54V supply rail) capable of supplying 4A to the
EV kit’s GND and VEE steel banana jacks or PCB pads.
A separate +3.3V power supply capable of supplying
100mA is also required for the IC’s optically isolated I
2
C-
compatible 2-wire interface if the USB interface circuit is
not used. Note: The DGND and VEE are shorted by a
0I resistor (R19). AGND and GND are shorted by a 0I
resistor (R68).
The IC controls the -48V/-54V DC power to each of the four
10/100/1000BASE-TX Ethernet output ports by regulating
the respective port’s n-channel power MOSFET and sens-
ing current through the respective port’s current-sense
resistors. The current is fed to the 10/100/1000BASE-TX
magnetic module connected to the respective Ethernet
output port’s RJ45 jack. An IEEE 802.3af/at-compliant
PD connects to the respective Ethernet output port (J2
upper ports) on the EV kit. The PD can be located up
to 350ft from the EV kit when connected with a twisted
4-pair Ethernet cable. The EV kit provides separate and
independent power control for each of the four Ethernet
output ports. The 10/100/1000BASE-TX magnetic module
is internally decoupled from the EV kit’s chassis ground.
Note: The EV kit’s isolated chassis ground (Chassis_
GND) PCB pad connects to the network system ground.
The EV kit features configurable operational modes,
PD detection, PD classification, overcurrent protection,
current foldback, under/overvoltage protection, DC dis-
connect monitoring, high-power mode, and port current
information through the I
2
C interface. The overcurrent pro-
tection can be programmed through the software. Each
of the four modes of operation (auto, semi, manual, and
shutdown) can be evaluated after configuring jumper JU6
and configuring the appropriate IC register (see Table 3),
or using the software’s high-level Configuration tab sheet
(see Figure 2). Each port features a 600W bidirectional
overvoltage-transient suppressor diode (D9–D12) and
decoupling capacitor (C26–C29) for transient protection
at the port.
Test points and jumpers have been provided for voltage
probing and current measurements of each channel’s
power circuit. Note: When using the header signals,
caution should be exercised since the DGND and VEE
are shorted by a 0I resistor (R19). AGND and GND are
shorted by a 0I resistor (R68). Additionally, since the
GND is more positive than VEE, use an isolated oscillo-
scope when probing signals with respect to VEE. Green
LEDs, relative to each port’s RJ45 output jack, indicate
when the respective port’s power is turned on.
The EV kit provides optical isolation for the I
2
C-
compatible 3-wire interface required by the IC operating
as a slave device with optocouplers U7 and U8. The
optically isolated interface connects to a computer’s
USB port through the USB interface circuit. The EV kit’s
I
2
C-compatible 2-wire or 3-wire interface can be recon-
figured for interfacing to a stand-alone microcontroller
for isolated (2-wire) or nonisolated (3-wire) serial opera-
tion. A separate +3.3V power supply capable of sup-
plying 100mA is required for the IC’s optically isolated
I
2
C-compatible 2-wire interface. Note: The DGND and
VEE are shorted by a 0I resistor (R19). AGND and GND
are shorted by a 0I resistor (R68).
The optical isolation consists of optocoupler U7, which
provides galvanic isolation for the serial-interface clock
line (SCL) and serial-interface input data line (SDAIN)
signals. Optocoupler U8 provides galvanic isolation
for the serial output and data line (SDAOUT) and INT
signals. The 3-wire serial interface SCL and SDAOUT
signals are combined on the isolated 2-wire side prior
to feeding logic buffer U9. The respective JU9 SCL_IN,
SDA, INT _OUT, OPTO_GND, and OPTO_VCC PCB pads
are used for 2-wire isolated stand-alone operation. For
nonisolated stand-alone 3-wire operation, jumper JU9
shorting traces must be cut open and then the SCL,
SDAIN, SDAOUT, INT , DGND, and VDIG PCB pads must
be connected to the microcontroller circuit. The VDIG is
set at +3.3V. The OPTO_GND, GND, and DGND planes
are isolated by the optocouplers. Note: When using the
EV kit in a nonisolated configuration, caution should be
exercised since the DGND and VEE are shorted by a
0I resistor (R19). AGND and GND are shorted by a 0I
resistor (R68). Additionally, since the GND is more posi-
tive than VEE, use an isolated oscilloscope when probing
signals with respect to VEE.
The IC slave address is configured by four jumpers
(JU1–JU4) and can be configured from 0x50 through
0x5F hexadecimal serial address. Global address 0x60
is accepted by the IC regardless of the jumper settings.
See Table 1 for more information on setting the IC
slave address.
Jumper Selection
The EV kit features several jumpers to reconfigure the EV
kit for various PSE configurations and PD requirements.
Additionally, jumpers and PCB pads are provided for
connecting an external microcontroller.
I
2
C-Compatible 2-Wire /3-Wire
Slave Address Selection
The EV kit features several 3-pin jumpers (JU1–JU4) to
set the slave address of the IC’s least-significant bits
(LSBs) of the slave address on the I
2
C-compatible 2-wire
or 3-wire interface. The three most-significant bits (MSBs)
are set by the IC to 010. The EV kit’s software automati-
cally sets the LSB for the proper read/write command.
Table 1 lists the jumper address options.