XIO3130
SLLS693F–MAY 2007–REVISED JANUARY 2010
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PCI Express Differential Transmitter Output Ranges (continued)
PARAMETER
TERMINALS
MIN NOM
MAX UNIT
COMMENTS
Maximum time to meet all TX specifications when
transitioning from electrical idle to sending
differential data. This value is considered a
de-bounce time for the TX to meet all TX
specifications after leaving electrical idle.
TTX-IDLE-to-DIFF-DATA
Maximum time to transition to valid
TX specifications after leaving an
electrical idle condition
PETP,
PETN
20
UI
RLTX-DIFF
Differential return loss
PETP,
PETN
Measured over 50 MHz to 1.25 GHz.
See
10
6
dB
dB
Ω
(5)
RLTX-CM
Common mode return loss
PETP,
PETN
Measured over 50 MHz to 1.25 GHz.
(5)
See
ZTX-DIFF-DC
DC differential TX impedance
PETP,
PETN
80
40
75
100
120
200
TX DC differential mode low impedance
ZTX-DC
PETP,
PETN
Required TX-D+ as well as TX-D– DC impedance
during all states
Ω
Transmitter DC impedance
CTX
PETP,
PETN
All transmitters are AC-coupled and capacitors are
required on the PWB.
nF
AC coupling capacitor
(5) The transmitter input impedance results in a differential return loss greater than or equal to 12 dB and a common mode return loss
greater than or equal to 6 dB over a frequency range of 50 MHz to 1.25 GHz. This input impedance requirement applies to all valid input
levels. The reference impedance for return loss measurements is 50 Ω to ground for both the P and N lines. Note that the series
capacitors CTX is optional for the return loss measurement.
6.4 PCI Express Differential Receiver Input Ranges
PARAMETER
TERMINALS
MIN NOM
MAX UNIT
COMMENTS
VRX-DIFFp-p
Differential input peak-to-peak
voltage
PERP,
PERN
VRX-DIFFp-p = 2*|VRX-D+ – VRX-D–|
See
0.175
1.2
V
(1)
The maximum interconnect media and transmitter
jitter that can be tolerated by the Receiver is
derived as TRX-MAX- JITTER = 1 - TRX-EYE = .6 UI
TRX-EYE
Minimum receiver eye width
PERP, PERN
0.4
UI
(1) (2) (3)
See
Jitter is defined as the measurement variation of
the crossing points (VRX-DIFFp-p = 0 V) in relation to
recovered TX UI. A recovered TX 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 TX UI.
TRX-EYE-MEDIAN-to-MAX-JITTER
Maximum time between the jitter
median and maximum deviation
from the median.
PERP,
PERN
0.3
UI
(1) (2)
See
VRX-CM-ACp = RMS( |VRX-D+ + VRX-D–| / 2 –
VRX-CM-DC)
VRX-CM-ACp
AC peak common mode input
voltage
PERP,
PERN
150
mV
VRX-CM-DC = DC(avg) of |VRX-D+ + VRX-D-| / 2
(1)
See
(1) Specified at the measurement point and measured using the clock recovery function specified in PCI Express™ Base Specification
Revision 1.1, Section 4.3.3.2. The test load in Figure 4-25 should be used as the RX device when taking measurements (also refer to
the Receiver compliance eye diagram shown in Figure 4-26 of the specification). If the clocks to the RX and TX are not derived from the
same reference clock, the TX UI recovered using the clock recovery function specified in Section 4.3.3.2 must be used as a reference
for the eye diagram.
(2) 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 0.64. 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. The RX
UI recovered using the clock recovery function specified in Section 4.3.3.2 must be used as the reference for the eye diagram. This
parameter is measured with the equivalent of a zero jitter reference clock. The TRX-EYE measurement is to be met at the target bit error
rate. The TRX-EYE-MEDIAN-to-MAX-JITTER specification is to be met using the compliance pattern at a sample size of 1,000,000 UI.
(3) See the PCI Express Jitter and BER white paper for more details on the Rx-Eye measurement.
136
Electrical Characteristics
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