Datasheet
0
50
100
150
200
250
0 10k 20k 30k 40k 50k 60k 70k 80k
SD_TH RESISTOR VALUE (:
)
ELECTRICAL IDLE DETECT THRESHOLD
(DIFF mVp-p)
V
DD
= 2.5V
T
A
= 25°C
DS50PCI401
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SNLS292J –JUNE 2009–REVISED APRIL 2013
Table 3. De-Emphasis Input Select Pins for A and B ports (3–Level Input) (continued)
RATE DEM1 DEM0
(1
Typical De- Typical DE Pulse
Typical VOD Suggested Use
(1) )
Emphasis Level Width
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
Table 4. Idle Control (3–Level Input)
TXIDLEA/B Function
0 This state is for lossy media, dedicated Idle threshold detect circuit disabled,
output follows input based on EQ settings. Idle state not guaranteed.
Float 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.
1 Manual override, output forced to Idle. Diff inputs are ignored.
Table 5. Receiver Electrical Idle Detect Threshold Adjust (Analog input - connect Resistor to GND or
Float)
SD_TH resistor value (Ω) (connect from pin to GND)
(1)
Typical Receiver Electrical Idle Detect Threshold (DIFF p-p)
Float (no resistor required) 130mV (default condition)
0 225mV
80K 20mV
(1) SD_TH resistor value can be set from 0 through 80K Ohms to achieve desired idle detect threshold, see Figure 1. 8K Ohm is approx
130mV.
Figure 1. Typical Idle threshold vs SD_TH resistor value
Table 6. Receiver Detect Pins for A and B ports (LVCMOS inputs)
PRSNT# ENRXDET RXDETA/B Function
0 1 0 Disable RXDETA termination mode: Rx detection state machine disabled. Input
termination >50KΩ. Associated output channels in low power idle mode.
0 1 1 Force RXDETA termination mode: Rx detection state machine disabled. Input termination
50Ω. Associated output channels set to active.
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