User's Manual

PW2050 Embedded Device Server Integration Guide 20

Note: The IO pins for PW2050 Wi-Fi SMT unit are set to floating input on power up until

configured by unit firmware. An external 100K ohm pull-up may be required on the serial transmit

signal to prevent downstream UART devices from detecting false characters on initial power up.

Ethernet Interface

The unit provides a 10/100 Mbps Ethernet interface for connection to an external network

through external magnetics and an external RJ45. The figure below shows the Ethernet

connections to a 10/100 Ethernet RJ45 Jack with Magnetics, J5 in the figure. The RJ45

Magnetic Jack is Belfuse part number 08B0-1D1T-06-F.

The Ethernet differential pair signals, ERXM/ERXP and ETXM/ETXP should be routed as 100-

ohm differential pairs on a layer next to the signal ground plane. The use of vias on these

signals should be minimized. Center tap signals RXCT and TXCT should be routed with at

least 20 mil trace thickness. The area underneath the RJ45 magnetic jack should be void of all

signals and planes. The connector shield should be connected to chassis. It is recommended

that 1206 resistor pads from chassis ground to signal ground be placed next to each of the

shield tabs. The resistor pads allow for 0 ohm jumper, ferrite beads, or decoupling caps to be

installed as needed for EMI/EMC improvement.

The Ethernet LED signals should be routed to discrete LEDs or to the LED pins on the RJ45

through 220 ohm or larger resistors. The LED signals are active low.

Also shown in the figure is an optional active choke that can be used to improve ESD, EFT,

and EMI/EMC performance in harsh environments. The device is shown as U22 in the figure

and is Akros part number AS1602. This device features route through pin assignments

allowing for the Ethernet differential signal pairs to be routed without altering the trace

impedance or adding vias. Due to this routing the device could be installed or depopulated as

needed. Lantronix has performed all certification to FCC Class B without U22 populated.

The Ethernet signals may be left unconnected if unused.

See the Lantronix app note, “How to Connect a Lantronix Embedded Module to a Wired

Ethernet Port” for more details on Ethernet connection and routing,

http://www.lantronix.com/pdf/appnotes/Connect-LTRX-Embed-Module-to-Wired-

Ethernet_AN.pdf.

Table 2-8 Ethernet Port Signals

Pin Name Description PW2050

Pins

Signal Requirement RJ45 MagJack

Belfuse, 08B0-

1D1T-06-F Pin

assignment

ERXM Ethernet Receive Negative signal. 41 100 ohm differential

pair with ERXP

EXRP Ethernet Receive Positive signal. 40 100 ohm differential

pair with ERXM

ETXM Ethernet Transmit Negative

signal.

35 100 ohm differential

pair with ETXP