Datasheet
Detailed Description of Hardware
Pasadena interfaces to powered Ethernet with an RJ-45 connector (J1). A second RJ-45 (J3) is present to
read data out of the system. The MAX5969B provides the complete interface to the Ethernet connection,
providing detection signature, classification signature, inrush current
control, and 2-event classification. The
MAX5969B also interfaces with a wall adaptor input, detecting the wall adaptor input and switching between
power sources. When present, a wall adaptor power source
always takes precedence over the power-
sourcing equipment (PSE) power, allowing the wall adaptor to power the reference design.
The MAX5974A provides up to 21W of galvanically isolated output power with current-mode PWM control
using a synchronous-rectified flyback DC-DC converter
topology. Both 3.3V and 5V outputs are available.
When connected to an IEEE 802.3af/at-compliant PSE, the reference design uses one of the two-channel,
full bridge rectifiers to convert the incoming -57V to DC. PCB pads V+ and V- are available for powering the
reference design if network-powered PSE is not available. The MAX5969B provides power to the DC-DC
circuit at the VDD and RTN pins. Configured for 21W of output power, Pasadena achieves 89.8% (V = 48V)
efficiency. The surface-mount transformer
and optocoupler provide up to 1500V of galvanic isolation.
Pasadena is configured for a Class 4 (12.95W to 25.5W) PD classification by resistor R4. To reconfigure the
PD classification, replace surface-mount (0805) resistor R4. Table 1 lists the PD classification options.
Table 1. PD Classification Selection
Class Maximum Power Used by PD Resistor R4 (Ω)
0 0.44 to 12.95 619
1 0.44 to 3.84 118
2 3.84 to 6.49 66.5
3 6.49 to 12.95 43.2
4 12.95 to 25.5 30.9
5 > 25.5 21.3
Pasadena can also accept power from a WAD. Connect positive and negative WAD power to the WAD+ and
WAD- connections, respectively. When WAD power exceeds 44V, WAD power takes precedence over PSE
power. The MAX5969B will internally disconnect VSS from RTN, when switching from PSE power to WAD
power. If WAD power drops below 40V, the MAX5969B will redetect and classify, then provide power from
the PSE through the device's RTN.
Pasadena features two modular RJ45 jacks (J1 and J3) to inter¬face with the Ethernet data signals. J1 is
provided for interfacing the reference design with the Ethernet data signals and PoE power. J3 is provided to
feed data back out of the system. Refer to the RJ45 magnetic jack data sheet on the Bel Fuse
website prior
to interfacing Pasadena's J1 and J3 modular RJ45 jack with the Ethernet data signals.
Quick Start
Caution: Do not turn on the power supply until all connections are completed.
Required equipment:
IEEE 802.3af/at-compliant PSE and Category 5e Ethernet network cable
-48V, 1A-capable DC power supply, if PSE is not available
Pasadena (MAXREFDES31#) board
Voltmeter
1. Use one of the following methods to power Pasadena:
If network connectivity is required: Connect a Category 5e Ethernet network cable from the
abovementioned PSE to the reference design input port RJ45 connector (J1). Optionally connect
an additional Category 5e Ethernet network cable to modular RJ45 jack (J3) to gather data that
passes through the Pasadena board.
If network connectivity is not required or unavailable, connect a -48V DC power supply between
the V+ and V- pads on the reference design. Connect the power-supply positive terminal to the
V+ pad and the negative terminal to the V- pad.
2. Connect the positive terminal of the voltmeter to the +3.3V connector at OUT1 of the MAXREFDES31#.
3. Connect the negative terminal of the voltmeter to the GND connector at OUT1 of the MAXREFDES31#.
IN