P5021 datasheet(113/155 Pages) NXP

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Electrical characteristics

P5021 QorIQ Integrated Processor Data Sheet, Rev. 1

Freescale Semiconductor

113

This table defines the AC specifications for the PCI Express 2.0 (2.5 GT/s) differential input at all receivers. The parameters are

specified at the component pins. The AC timing specifications do not include RefClk jitter.

Table 68. PCI Express 2.0 (2.5 GT/s) differential receiver Input AC specifications

For recommended operating conditions, see Table 3.

Parameter

Symbol

Min

Typ

Max

Units

Notes

Unit Interval

399.88 400.00 400.12

Each UI is 400 ps ± 300 ppm. UI does not

account for spread spectrum clock dictated

variations. See Note 1.

Minimum receiver eye width

TRX-EYE

0.4

—

The maximum interconnect media and

transmitter jitter that can be tolerated by the

receiver can be derived as

TRX-MAX-JITTER =1 – TRX-EYE= 0.6 UI.

See Notes 2 and 3.

Maximum time between the

jitter median and maximum

deviation from the median.

TRX-EYE-MEDIAN-

to-MAX-JITTER

—

0.3

Jitter is defined as the measurement

variation of the crossing points

(VRX-DIFFp-p = 0 V) in relation to a recovered

transmitter UI. A recovered transmitter UI is

calculated over 3500 consecutive unit

intervals of sample data. Jitter is measured

using all edges of the 250 consecutive UI in

the center of the 3500 UI used for calculating

the transmitter UI.

See Notes 2, 3 and 4.

Notes:

1. No test load is necessarily associated with this value.

2. Specified at the measurement point and measured over any 250 consecutive UIs. The test load in Figure 43 should be used

as the receiver device when taking measurements. If the clocks to the receiver and transmitter are not derived from the same

reference clock, the transmitter UI recovered from 3500 consecutive UI must be used as a reference for the eye diagram.

3. A TRX-EYE = 0.40 UI provides for a total sum of 0.60 UI deterministic and random jitter budget for the transmitter and

interconnect collected any 250 consecutive UIs. The TRX-EYE-MEDIAN-to-MAX-JITTER specification ensures a jitter

distribution in which the median and the maximum deviation from the median is less than half of the total. UI jitter budget

collected over any 250 consecutive transmitter UIs. It should be noted that the median is not the same as the mean. The jitter

median describes the point in time where the number of jitter points on either side is approximately equal as opposed to the

averaged time value. If the clocks to the receiver and transmitter are not derived from the same reference clock, the transmitter

UI recovered from 3500 consecutive UI must be used as the reference for the eye diagram.

4. It is recommended that the recovered transmitter UI is calculated using all edges in the 3500 consecutive UI interval with a fit

algorithm using a minimization merit function. Least squares and median deviation fits have worked well with experimental

and simulated data.

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