DS50PCI402_14 Datasheet, PDF (7/35 Pages) Texas Instruments – 2.5 Gbps / 5.0 Gbps 4 Lane PCI Express Repeater with Equalization and De-Emphasis

DS50PCI402
www.ti.com
SNLS320G – APRIL 2010 – REVISED MAY 2011
Table 4. De-Emphasis Input Select Pins for A and B ports (3–Level Input) (continued)
RATE
DEM1 DEM0
Typical De-
Typical DE Pulse
Emphasis Level
Width
Typical VOD
Suggested Use
0/F
F
1
-12dB
400ps enhanced
1400mV
40 inches FR4 (6-mil trace)
0/F
F
F
Reserved, don't
use
1/F
0
0
0dB
0ps
1000mV
1/F
0
1
-3.5dB
200ps
1000mV
1/F
1
0
-6dB
200ps
1000mV
1/F
1
1
-6dB
200ps enhanced
1000mV
10 inches FR4 (6-mil trace)
1/F
0
F
-9dB
200ps enhanced
1000mV
1/F
1
F
-12dB
200ps enhanced
1000mV
1/F
F
0
-9dB
200ps enhanced
1200mV
20 inches FR4 (6-mil trace)
1/F
F
1
-12dB
200ps enhanced
1400mV
30 inches FR4 (6-mil trace)
1/F
F
F
Reserved, don't
use
F=Float (don't drive pin - (each float pin has an internal 50K Ohm resistor to VDD and GND). Enhanced DE Pulse width provides additional
de-emphasis on second bit. VOD = Voltage Output Differential amplitude. When RATE is floated (F=Auto Rate Detection Active) DE Level
and Pulse Width settings follow detected RATE. RATE=0 is 2.5GBps, RATE=1 is 5 GBps
TXIDLEA/B
0
Float
1
Table 5. Idle Control (3–Level Input)
Function
This state is for lossy media, dedicated Idle threshold detect circuit disabled,
output follows input based on EQ settings. Idle state not guaranteed.
Float enables automatic idle detection. Idle on the input is passed to the
output. This is the recommended default state. Output driven to Idle if diff input
signal less than value set by SD_TH pin.
Manual override, output forced to Idle. Diff inputs are ignored.
Table 6. Receiver Electrical Idle Detect Threshold Adjust (Analog input - Connect Resistor to GND or
Float)
SD_TH resistor value (Ω) (connect from pin to GND)
Typical Receiver Electrical Idle Detect Threshold (DIFF p-p)
Float (no resistor required)
130mV (default condition)
0
225mV
80K
20mV
SD_TH resistor value can be set from 0 through 80K Ohms to achieve desired idle detect threshold, see Figure 2. 8K Ohm is approx
130mV.
250
V_DD = 2.5V
T_A = 25°C
200
150
100
50
0
0 10k 20k 30k 40k 50k 60k 70k 80k
SD_TH RESISTOR VALUE (:)
Figure 2. Typical Idle threshold vs SD_TH resistor value
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