DS50PCI401 Datasheet, PDF (6/32 Pages) National Semiconductor (TI) – 2.5 Gbps / 5.0 Gbps 4 Lane PCI Express Transceiver with Equalization and De-Emphasis

SMBUS Mode:
When in SMBus mode the equalization, de-emphasis, and
termination disable features are all programmable on a indi-
vidual lane basis, instead of grouped by sides as in the pin
mode case. Upon assertion of ENSMB the RATE, EQx and
DEMx functions revert to register control immediately. The
EQx and DEMx pins are converted to AD0-AD3 SMBus ad-
dress inputs. The other external control pins remain active
unless their respective registers are written to and the appro-
priate override bit is set, in which case they are ignored until
ENSMB is driven low. On powerup and when ENSMB is driv-
en low all registers are reset to their default state. If PRSNT
is asserted while ENSMB is high, the registers retain their
current state.
TABLE 1. Equalization Input Select Pins for A and B ports (3–Level Input)
EQ1
EQ0
Equalization Level
Suggested Use
F
F
Off
Bypass
1
1
Approx. 4 dB at 2.5Ghz
8 inches FR4 (6-mil trace) or less than 1 meter (28 AWG) PCIe
cable
0
0
Approx. 9.6 dB at 2.5GHz
14 inches FR4 (6-mil trace) or 1 meter (28 AWG) PCIe cable
F
0
Approx. 11.4 dB at 2.5Ghz
20 inches FR4 (6-mil trace) or 5 meters (26 AWG) PCIe cable
1
0
Approx. 15.5 dB at 2.5Ghz
30 inches FR4 (6-mil trace) or 7 meters (24 AWG) PCIe cable
F
1
Approx. 17 dB at 2.5Ghz
40 inches FR4 (6-mil trace) or 9 meters (24 AWG) PCIe cable
0
1
Approx.19.1 dB at 2.5Ghz 50 inches FR4 (6-mil trace) or 10 meters (24 AWG) PCIe cable
0
F
Approx. 20.6 dB at 2.5Ghz
15 meters (24 AWG) PCIe cable
1
F
Approx. 26.3 dB at 2.5Ghz
>15 meters (24 AWG) PCIe cable
F=Float (don't drive pin, each float pin has an internal 50K Ohm resistor to VDD and GND), 1=High, 0=Low
TABLE 2. 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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