PCI Express
Table 52. Differential Transmitter (TX) Output Specifications (continued)
Symbol
V
TX-DE-RATIO
Parameter
De- emphasized
differential
output voltage
(ratio)
Minimum TX eye
width
Maximum time
between the
jitter median and
maximum
deviation from
the median.
Min
–3.0
Nom
–3.5
Max
–4.0
Unit
dB
Comments
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 2.
The maximum transmitter jitter can be derived as
T
TX-MAX-JITTER
= 1 – T
TX-EYE
= 0.3 UI.
See Notes 2 and 3.
Jitter is defined as the measurement variation of
the crossing points (V
TX-DIFFp-p
= 0 V) in relation
to a 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.
See Notes 2 and 3.
See Notes 2 and 5.
V
TX-CM-ACp
= RMS(|V
TXD+
+ V
TXD–
|/2 –
V
TX-CM-DC
)
V
TX-CM-DC
= DC
(avg)
of |V
TX-D+
+ V
TX-D–
|/2.
See Note 2.
|V
TX-CM-DC (during L0)
+ V
TX-CM-Idle-DC (during
electrical idle)
|
≤
100 mV
V
TX-CM-DC
= DC
(avg)
of |V
TX-D+
+ V
TX-D–
|/2 [L0]
V
TX-CM-Idle-DC
= DC
(avg)
of |V
TX-D+
+ V
TX-D–
|/2
[electrical idle]
See Note 2.
|V
TX-CM-DC-D+
– V
TX-CM-DC-D–
|
≤
25 mV
V
TX-CM-DC-D+
= DC
(avg)
of |V
TX-D+
|
V
TX-CM-DC-D–
= DC
(avg)
of |V
TX-D–
|.
See Note 2.
V
TX-IDLE-DIFFp
= |V
TX-IDLE-D+
– V
TX-IDLE-D–
|
≤
20 mV.
See Note 2.
The total amount of voltage change that a
transmitter can apply to sense whether a low
impedance receiver is present. See Note 6.
T
TX-EYE
0.70
—
—
UI
T
TX-EYE-MEDIAN-to-
MAX-JITTER
—
—
0.15
UI
T
TX-RISE
, T
TX-FALL
V
TX-CM-ACp
D+/D– TX output
rise/fall time
RMS AC peak
common mode
output voltage
Absolute delta of
dc common
mode voltage
during L0 and
electrical idle
0.125
—
—
—
—
20
UI
mV
V
TX-CM-DC-ACTIVE-
IDLE-DELTA
0
—
100
mV
V
TX-CM-DC-LINE-DELTA
Absolute delta of
DC common
mode between
D+ and D–
V
TX-IDLE-DIFFp
Electrical idle
differential peak
output voltage
The amount of
voltage change
allowed during
receiver
detection
The TX DC
common mode
voltage
TX short circuit
current limit
0
—
25
mV
0
—
20
mV
V
TX-RCV-DETECT
—
—
600
mV
V
TX-DC-CM
0
—
3.6
V
The allowed DC common mode voltage under any
conditions. See Note 6.
The total current the transmitter can provide when
shorted to its ground
I
TX-SHORT
—
—
90
mA
MPC8548E PowerQUICC™ III Integrated Processor Hardware Specifications, Rev. 6
70
Freescale Semiconductor
FREESCALE [ FREESCALE SEMICONDUCTOR, INC ]
