DS50PCI402 Datasheet, PDF (8/36 Pages) Texas Instruments – DS50PCI402 2.5 Gbps / 5.0 Gbps 4 Lane PCI Express Repeater with Equalization and De-Emphasis

TABLE 3. Equalization Settings with GST=3 for Pins or SMBus Registers
EQ Setting
EQ Gain (dB)
EQ1 EQ0 GST BST 1.25 GHz
2.5 GHz
Suggested Use
[1:0] [2:0]
11 000
6.4
12.2
1 0 11 001
8.5
15.6
30" FR4 (6-mil trace) or 7m (24 AWG) PCIe cable
11 010
10.4
18.3
0 F 11 011
12.4
21.3
15m (24 AWG) PCIe cable
11 100
15.2
25.0
1 F 11 101
18.1
27.2
> 15m (24 AWG) PCIe cable
11 110
19.6
28.8
11 111
20.2
30.7
F=Float (don't drive pin, each float pin has an internal 50K Ohm resistor to VDD and GND), 1=High, 0=Low
The De-Emphasis level must be set when in SMBus
mode. See SMBus TRANSACTIONS section and Table 9
for specific De-Emphasis values.
TABLE 4. De-Emphasis Input Select Pins for A and B ports (3–Level Input)
RATE DEM1 DEM0 Typical De- Typical DE Pulse
Emphasis Level
Width
Typical VOD
Suggested Use
0/F
0
0
0dB
0ps
1000mV
0/F
0
1
-3.5dB
400ps
1000mV
8 inches FR4 (6-mil trace) or less than 1
meter (28 AWG) PCIe cable
0/F
1
0
-6dB
400ps
1000mV
0/F
1
1
-6dB
400ps enhanced
1000mV
15 inches FR4 (6-mil trace)
0/F
0
F
-9dB
400ps enhanced
1000mV
0/F
1
F
-12dB
400ps enhanced
1000mV
0/F
F
0
-9dB
400ps enhanced
1200mV
30 inches FR4 (6-mil trace)
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
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