ORSPI4 datasheet(187/263 Pages) LATTICE

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Lattice Semiconductor

ORCA ORSPI4 Data Sheet

187

Input Eye-Mask Characterization

Figure 97 provides an eye-mask characterization of the SERDES receiver input. The eye-mask is speciﬁed below

for two different eye-mask heights. It provides guidance on a number of input parameters, including signal ampli-

tude and rise time limits, noise and jitter limits, and P and N input skew tolerance. Almost all detrimental character-

istics of transmit signal and the interconnection link design result in eye-closure. This, combined with the eye-

opening limitations of the line receiver, can provide a good indication of a link’s ability to transfer data error-free.

The Clock and Data Recovery (CDR) portion of the ORSPI4 SERDES receiver has the ability to ﬁlter incoming sig-

nal jitter that is below the clock recovery PLL bandwidth (about 3 MHz). The eye-mask speciﬁcations of Table 70

are for jitter frequencies above the PLL bandwidth of the CDR, which is a worst case condition. When jitter occurs

at frequencies below the PLL bandwidth, the receiver jitter tolerance is signiﬁcantly better. For this case error-free

data detection can occur even with a completely closed eye-mask.

Figure 97. Receive Data Eye-Diagram Template (Differential)

Table 70. Receiver Eye-Mask Speciﬁcations1

Parameter

Conditions

Value

Unit

Input Data

Eye Opening Width (H) @ 3.125 Gbps

V=175 mV diff

0.55

UIP-P

Eye Opening Width (T) @ 3.125 Gbps

V=175 mV diff

0.15

UIP-P

Eye Opening Width (H) @ 3.125 Gbps

V=600 mV diff

0.35

UIP-P

Eye Opening Width (T) @ 3.125 Gbps

V=600 mV diff

0.10

UIP-P

Eye Opening Width (H) @ 2.5 Gbps

V=175 mV diff

0.42

UIP-P

Eye Opening Width (T) @ 2.5 Gbps

V=175 mV diff

0.15

UIP-P

Eye Opening Width (H) @ 2.5 Gbps

V=600 mV diff

0.33

UIP-P

Eye Opening Width (T) @ 2.5 Gbps

V=600 mV diff

0.10

UIP-P

1. With PRBS 2^7-1 data pattern, 10 MHz sinusoidal jitter, all channels operating, FPGA logic active, REFCLK jitter

of 30 ps., TA = 0

oC to 85oC, 1.425 V to 1.575 V supply.

1.2 V

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