P5021 datasheet(102/155 Pages) NXP

102 / 155 page

P5021 QorIQ Integrated Processor Data Sheet, Rev. 1

Electrical characteristics

Freescale Semiconductor

102

This figure shows how the signals are defined. For illustration purposes only, one SerDes lane is used in the description. This

figure shows the waveform for either a transmitter output (SD_TXn and SD_TXn) or a receiver input (SD_RXn and SD_RXn).

Each signal swings between A volts and B volts where A > B.

Figure 35. Differential voltage definitions for transmitter or receiver

Using this waveform, the definitions are as shown in the following list. To simplify the illustration, the definitions assume that

the SerDes transmitter and receiver operate in a fully symmetrical differential signaling environment:

Single-Ended Swing

The transmitter output signals and the receiver input signals SD_TXn, SD_TXn, SD_RXn and

SD_RXn each have a peak-to-peak swing of A – B volts. This is also referred as each signal wire’s

single-ended swing.

Differential Output Voltage, VOD (or Differential Output Swing):

The differential output voltage (or swing) of the transmitter, VOD, is defined as the difference of

the two complementary output voltages: VSD_TXn – VSD_TXn. The VOD value can be either

positive or negative.

Differential Input Voltage, VID (or Differential Input Swing):

The differential input voltage (or swing) of the receiver, VID, is defined as the difference of the two

complementary input voltages: VSD_RXn – VSD_RXn. The VID value can be either positive or

negative.

Differential Peak Voltage, VDIFFp

The peak value of the differential transmitter output signal or the differential receiver input signal

is defined as the differential peak voltage, VDIFFp = |A – B| volts.

Differential Peak-to-Peak, VDIFFp-p

Since the differential output signal of the transmitter and the differential input signal of the receiver

each range from A – B to –(A – B) volts, the peak-to-peak value of the differential transmitter

output signal or the differential receiver input signal is defined as differential peak-to-peak voltage,

VDIFFp-p = 2 × VDIFFp = 2 × |(A – B)| volts, which is twice the differential swing in amplitude, or

twice of the differential peak. For example, the output differential peak-peak voltage can also be

calculated as VTX-DIFFp-p = 2 × |VOD|.

Differential Waveform

The differential waveform is constructed by subtracting the inverting signal (SD_TXn, for

example) from the non-inverting signal (SD_TXn, for example) within a differential pair. There is

only one signal trace curve in a differential waveform. The voltage represented in the differential

Differential Swing, VID or VOD = A – B

A Volts

B Volts

SD_TXn

SD_RXn

SD_TXn

SD_RXn

Differential Peak Voltage, VDIFFp = |A – B|

Differential Peak-Peak Voltage, VDIFFpp = 2 × VDIFFp (not shown)

Vcm = (A + B)/2

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