Datasheet

Electrical Characteristics
177
March 5 2007 − June 2011 SCPS154C
11.3 PCI Express Differential Transmitter Output Ranges
PARAMETER TERMINALS MIN NOM MAX UNITS COMMENTS
UI
Unit interval
TXP, TXN 399.88 400 400.12 ps
Each UI is 400 ps ±300 ppm. UI does not account
for SSC dictated variations.
See Note 4.
V
TX-DIFFp-p
Differential peak-to-peak
output voltage
TXP, TXN 0.8 1.2 V
V
TX-DIFFp-p
= 2*|V
TXP
− V
TXN
|
See Note 5.
V
TX-DE-RATIO
De-emphasized
differential output voltage
(ratio)
TXP, TXN −3.0 −3.5 −4.0 dB
This is the ratio of the V
TX-DIFFp-p
of the second
and following bits after a transition divided by the
V
TX-DIFFp-p
of the first bit after a transition.
See Note 5.
T
TX-EYE
Minimum TX eye width
TXP, TXN 0.75 UI
The maximum transmitter jitter can be derived as
T
TXMAX- JITTER
= 1 − T
TX-EYE
= 0.3 UI
See Notes 5 and 6.
T
TX-EYE-MEDIAN-to-MAX-JITTER
Maximum time between the
jitter median and maximum
deviation from the median
TXP, TXN 0.15 UI
Jitter is defined as the measurement variation of
the crossing points (V
TX-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 5 and 6.
T
TX-RISE
,
T
TX-FALL
P/N TX output rise/fall time
TXP, TXN 0.125 UI See Notes 5 and 8.
V
TX-CM-ACp
RMS ac peak common mode
output voltage
TXP, TXN 20 mV
V
TX-CM-ACp
= RMS(|V
TXP
+ V
TXN
|/2 – V
TX-CM-DC
)
V
TX-CM-DC
= DC
(avg)
of |V
TXP
+ V
TXN
|/2
See Note 5.
V
TX-CM-DC-ACTIVE-IDLE-DELTA
Absolute delta of dc common
mode voltage during L0 and
electrical idle.
TXP, TXN 0 100 mV
|V
TX-CM-DC
– V
TX-CM-Idle-DC
| ≤ 100 mV
V
TX-CM-DC
= DC
(avg)
of |V
TXP
+ V
TXN
|/2 [during
L0]
V
TX-CM-Idle-DC
= DC
(avg)
of |V
TXP
+ V
TXN
|/2
[during electrical idle]
See Note 5.
V
TX-CM-DC-LINE-DELTA
Absolute delta of dc common
mode voltage between P and
N
TXP, TXN 0 25 mV
|V
TXP-CM-DC
– V
TXN-CM-DC
| ≤ 25 mV when
V
TXP-CM-DC
= DC
(avg)
of |V
TXP
|
V
TXN-CM-DC
= DC
(avg)
of |V
TXN
|
See Note 5.
V
TX-IDLE-DIFFp
Electrical idle differential peak
output voltage
TXP, TXN 0 20 mV
V
TX-IDLE-DIFFp
= |V
TXP-Idle
− V
TXN-Idle
| ≤ 20 mV
See Note 5.
V
TX-RCV-DETECT
The amount of voltage
change allowed during
receiver detection
TXP, TXN 600 mV
The total amount of voltage change that a
transmitter can apply to sense whether a low
impedance receiver is present.
V
TX-DC-CM
The TX dc common mode
voltage
TXP, TXN 0 3.6 V
The allowed dc common mode voltage under any
condition.
Not Recommended for New Designs