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