Datasheet

Electrical Characteristics
179
March 5 2007 − June 2011 SCPS154C
11.4 PCI Express Differential Receiver Input Ranges
PARAMETER TERMINALS MIN NOM MAX UNITS COMMENTS
UI
Unit interval
RXP, RXN 399.88 400 400.12 ps
Each UI is 400 ps ±300 ppm. UI does not account for
SSC dictated variations.
See Note 9.
V
RX-DIFFp-p
Differential input
peak-to-peak voltage
RXP, RXN 0.175 1.200 V
V
RX-DIFFp-p
= 2*|V
RXP
− V
RXN
|
See Note 10.
T
RX-EYE
Minimum receiver eye width
RXP, RXN 0.4 UI
The maximum interconnect media and transmitter jitter
that can be tolerated by the receiver is derived as
T
RX-MAX-JITTER
= 1 − T
RX-EYE
= 0.6 UI
See Notes 10 and 11.
T
RX-EYE-MEDIAN-to-MAX-JITTER
Maximum time between the
jitter median and maximum
deviation from the median
RXP, RXN 0.3 UI
Jitter is defined as the measurement variation of the
crossing points (V
RX-DIFFp-p
= 0 V) in relation to
recovered TX UI. A recovered TX UI is calculated over
3500 consecutive UIs of sample data. Jitter is
measured using all edges of the 250 consecutive UIs
in the center of the 3500 UIs used for calculating the
TX UI.
See Notes 10 and 11.
V
RX-CM-ACp
AC peak common mode input
voltage
RXP, RXN 150 mV
V
RX-CM-ACp
= RMS(|V
RXP
+ V
RXN
|/2 – V
RX-CM-DC
)
V
RX-CM-DC
= DC
(avg)
of |V
RXP
+ V
RXN
|/2
See Note 10.
RL
RX-DIFF
Differential return loss
RXP, RXN 10 dB
Measured over 50 MHz to 1.25 GHz with the P and N
lines biased at +300 mV and −300 mV, respectively.
See Note 12.
RL
RX-CM
Common mode return loss
RXP, RXN 6 dB
Measured over 50 MHz to 1.25 GHz with the P and N
lines biased at +300 mV and −300 mV, respectively.
See Note 12.
Z
RX-DIFF-DC
DC differential input
impedance
RXP, RXN 80 100 120 Ω
RX dc differential mode impedance
See Note 13.
Z
RX-DC
DC input impedance
RXP, RXN 40 50 60 Ω
Required RXP as well as RXN dc impedance (50 Ω
±20% tolerance).
See Notes 10 and 13.
Z
RX-HIGH-IMP-DC
Powered down dc input
impedance
RXP, RXN 200k Ω
Required RXP as well as RXN dc impedance when the
receiver terminations do not have power.
See Note 14.
V
RX-IDLE-DET-DIFFp-p
Electrical idle detect
threshold
RXP, RXN 65 175 mV
V
RX-IDLE-DET-DIFFp-p
= 2*|V
RXP
− V
RXN
| measured at
the receiver package terminals
T
RX-IDLE-DET-DIFF-ENTER-TIME
Unexpected electrical idle
enter detect threshold
integration time
RXP, RXN 10 ms
An unexpected electrical idle (V
RX-DIFFp-p
<
V
RX-IDLE-DET-DIFFp-p
) must be recognized no longer
than T
RX-IDLE-DET-DIFF-ENTER-TIME
to signal an
unexpected idle condition.
NOTES: 9. No test load is necessarily associated with this value.
10. Specified at the measurement point and measured over any 250 consecutive UIs. A test load must be used as the RX device when
taking measurements. If the clocks to the RX and TX are not derived from the same reference clock, then the TX UI recovered from
3500 consecutive UI is used as a reference for the eye diagram.
Not Recommended for New Designs