USB3250

DS00002142A-page 16

6.2

Hi-Speed Signaling Eye Patterns

Hi-Speed USB signals are characterized using eye patterns. For measuring the eye patterns 4 points have been defined

(see Figure 6-3). The Universal Serial Bus Specification Rev.2.0 defines the eye patterns in several 'templates'. The two

templates that are relevant to the PHY are shown below.

The eye pattern in Figure 6-4 defines the transmit waveform requirements for a hub (measured at TP2 of Figure 6-3) or

a device without a captive cable (measured at TP3 of Figure 6-3). The corresponding signal levels and timings are given

in Table 6-6. Time is specified as a percentage of the unit interval (UI), which represents the nominal bit duration for a

480 Mbit/s transmission rate.

FIGURE 6-3:

EYE PATTERN MEASUREMENT PLANES

USB

Transceiver

Device Circuit Board

Transceiver

Hub Circuit Board

Connector

Traces

Traces

A

Connector

B

TP1

TP2

TP3

TP4