Miniature 10 Base-T Isolation Transformer ELECTRONICS INC. EPE6289S • Optimized for Level One LXT905 • • Robust design allows for toughest soldering processes • • Small outline package on 0.050” pitch • • Complies with or exceeds IEEE 802.3, 10 Base-T Requirements • Electrical Parameters @ 25° C Cable Side Inductance (µH Min.) Interwinding Capacitance (pF Max.) Leakage Inductance (µH Max.) Insertion Loss (dB Max.) Return Loss (dB Min.) @ 100 KHz, 0.1 Vrms @ 100 KHz, 0.1 Vrms @ 100 KHz, 0.1 Vrms 1-20 MHz 5-10 MHz 12 0.3 -1 -20 Hipot (Vrms) Rcv Xmit 200 200 1500 Transceiver Side DCR (Ω Max.) Xmit 0.35 Rcv 0.50 Schematic Transmit 1:2 6 Receive 1:1 11 Transceiver Side 1 Cable Side 8 16 Transceiver Side Cable Side 9 14 3 Package A (J) PCA EPE6289S Date Code (Inches) Suggested Solder Pad Layout B Dim. Min. Max. A B C D E F G H I (J) K L M N P Q .480 .260 .180 .350 .005 .050 .370 .016 .010 .070 0° .025 .500 .280 .200 Typ. .015 Typ. .390 .022 Typ. Typ. 8° .045 Q M D C E H Dimensions N P F K I L Nom. .030 .050 .055 .410 (millimeters) Min. Max. Nom. 12.19 6.60 4.57 8.89 .127 1.27 9.40 .406 .254 1.78 0° .635 12.70 7.11 5.08 Typ. .381 Typ. 9.91 .559 Typ. Typ. 8° 1.14 .762 1.27 1.40 10.41 G PCA ELECTRONICS, INC 16799 SCHOENBORN ST. NORTH HILLS, CA 91343 CSE6289Sa Rev. 1 4/14/97 TEL: (818) 892-0761 FAX: (818) 894-5791 http://www.pcainc.com 10 Base-T Interface Module EPE6289S ELECTRONICS INC. The circuit below is a guideline for interconnecting PCA’s EPE6289S with LXT905 10 Base-T PHY chip over UTP cable. Further details of system design, such as chip pin-out, etc. can be obtained from the specific chip manufacturer. Typical insertion loss of the isolation transformer is 0.7dB. This parameter covers the entire spectrum of the encoded signals in 10 Base-T protocols. However, the predistortion resistor network introduces some loss which has to be taken into account in determining how well your design meets the Standard Template requirements. Additionally, the following need to be considered while selecting resistor values : a. Each channel needs 100Ω termination, thus the Thevenin’s equivalent resistance seen by a channel looking into the transmit outputs from the chip must be equal to a value close to 100Ω. The LXT 905 driver output impedances are very low. . Thus only 11.8Ω on TPON & TPOP are enough to provide a balanced 25 Ω termination given that turns ratio is 1:2. Following these guidelines will guarantee that the return loss specifications are satisfied at all extremes of cable impedance (i.e. 85Ω to 115Ω) while the module is installed in your system. The receiver channel termination is rather straight forward: two 50Ω loads provide the balanced termination to the cable. b. That the template requirements are satisfied under the worst case Vcc (i.e. 4.5V), will impose a further constraint on resistor selection, in that they ought to be the minimum derived from the calculations. Users can allow for pads on their PCB for a shunting resistor across pins 6 and 8 of EPE6289S for more flexibility in setting voltage levels at the outputs. Note that some systems have auto polarity detection and some do not. If not, be certain to follow the proper polarity. The pulldown resistors used around the RJ45 connector have been known to suppress unwanted radiation that unused wires pick up from the immediate environment. Their placement and use are to be considered carefully before a design is finalized. It is recommended that there be a neat separation of ground planes in the layout. It is generally accepted practice to limit the plane off at least 0.08 inches away from the chip side pins of EPE6289S. There need not be any ground plane beyond this point. For best results, PCB designer should design the outgoing traces preferably to be 50Ω, balanced and well coupled to achieve minimum radiation from these traces. Typical Application Circuit for UTP with external Resistor Network 1 TPIN 9 1 11 2 14 3 16 6 EPE6289S LXT905 PHY 3 TPIP TX+ TX- RJ45* RX+ RX4 6 5 7 8 8 TPON TPOP High voltage cap, if used 2KV recommended .1uF X7R Chassis Ground Notes : * Pin-outs shown are for NIC configurations. For Hubs and Repeaters swap pins 1-2 with pins 3-6. PCA ELECTRONICS, INC. 16799 SCHOENBORN ST. NORTH HILLS, CA 91343 CSE6289Sb Rev. 1 4/14/97 TEL: (818) 892-0761 FAX: (818) 894-5791 http://www.pcainc.com