KSZ8051MNLV Datasheet, PDF (62/66 Pages) Micrel Semiconductor – 10Base-T/100Base-TX Physical Layer Transceiver

Micrel, Inc.
KSZ8051MNLV/KSZ8051RNLV
Magnetics – Connection and Selection
A 1:1 isolation transformer is required at the line interface. Use one with integrated common-mode chokes for designs
exceeding FCC requirements.
The KSZ8051MNLV/RNLV design incorporates voltage-mode transmit drivers and on-chip terminations.
With the voltage-mode implementation, the transmit drivers supply the common-mode voltages to the two differential
pairs. Therefore, the two transformer center tap pins on the KSZ8051MNLV/RNLV side should not be connected to any
power supply source on the board; instead, the center tap pins should be separated from one another and connected
through separate 0.1µF common-mode capacitors to ground. Separation is required because the common-mode voltage
is different between transmitting and receiving differential pairs.
Figure 26 shows the typical magnetic interface circuit for the KSZ8051MNLV/RNLV.
Figure 26. Typical Magnetic Interface Circuit
August 27, 2015
62
Revision 1.0