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KSZ9031RNX

Gigabit Ethernet Transceiver with RGMII Support

Microchip Technology 

KSZ9031RNX

3.0 FUNCTIONAL DESCRIPTION

The KSZ9031RNX is a completely integrated triple-speed (10BASE-T/100BASE-TX/1000BASE-T) Ethernet physical

layer transceiver solution for transmission and reception of data over a standard CAT-5 unshielded twisted pair (UTP)

cable.

The KSZ9031RNX reduces board cost and simplifies board layout by using on-chip termination resistors for the four

differential pairs and by integrating an LDO controller to drive a low-cost MOSFET to supply the 1.2V core.

On the copper media interface, the KSZ9031RNX can automatically detect and correct for differential pair misplace-

ments and polarity reversals, and correct propagation delays and re-sync timing between the four differential pairs, as

specified in the IEEE 802.3 standard for 1000BASE-T operation.

The KSZ9031RNX provides the RGMII interface for connection to RGMII MACs in Gigabit Ethernet processors and

switches for data transfer at 10/100/1000 Mbps.

Figure 3-1 shows a high-level block diagram of the KSZ9031RNX.

FIGURE 3-1:

KSZ9031RNX BLOCK DIAGRAM

MEDIA

INTERFACE

PMA

TX 10 /100 /1000

PMA

RX1000

PMA

RX100

CLOCK

RESET

CONFIGURATIONS

PCS 1000

PCS 100

RGMII

INTERFACE

PMA

RX10

PCS 10

AUTO-

NEGOTIATION

LED

DRIVERS

3.1 10BASE-T/100BASE-TX Transceiver

3.1.1 100BASE-TX TRANSMIT

The 100BASE-TX transmit function performs parallel-to-serial conversion, 4B/5B coding, scrambling, NRZ-to-NRZI con-

version, and MLT-3 encoding and transmission.

The circuitry starts with a parallel-to-serial conversion, which converts the MII data from the MAC into a 125 MHz serial

bit stream. The data and control stream is then converted into 4B/5B coding, followed by a scrambler. The serialized

data is further converted from NRZ-to-NRZI format, and then transmitted in MLT-3 current output. The output current is

set by an external 12.1 kΩ 1% resistor for the 1:1 transformer ratio.

The output signal has a typical rise/fall time of 4 ns and complies with the ANSI TP-PMD standard regarding amplitude

balance, and overshoot. The wave-shaped 10BASE-T output is also incorporated into the 100BASE-TX transmitter.

3.1.2 100BASE-TX RECEIVE

The 100BASE-TX receiver function performs adaptive equalization, DC restoration, MLT-3-to-NRZI conversion, data

and clock recovery, NRZI-to-NRZ conversion, de-scrambling, 4B/5B decoding, and serial-to-parallel conversion.

The receiving side starts with the equalization filter to compensate for inter-symbol interference (ISI) over the twisted

pair cable. Because the amplitude loss and phase distortion are a function of the cable length, the equalizer must adjust

its characteristics to optimize performance. In this design, the variable equalizer makes an initial estimation based on

comparisons of incoming signal strength against some known cable characteristics, then tunes itself for optimization.

This is an ongoing process and self-adjusts against environmental changes such as temperature variations.

 2016 Microchip Technology Inc.

DS00002117C-page 13

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