DS50PCI402 Datasheet, PDF (9/36 Pages) Texas Instruments – DS50PCI402 2.5 Gbps / 5.0 Gbps 4 Lane PCI Express Repeater with Equalization and De-Emphasis

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 1. 8K Ohm is
approx 130mV.
30107393
FIGURE 1. Typical Idle threshold vs SD_TH resistor value
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