DS64BR401 Datasheet, PDF (14/30 Pages) National Semiconductor (TI) – Quad Bi-Directional Transceiver with Equalization and De-Emphasis

TXIDLEA/B
0
Float
1
TABLE 3. 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. Internal 50KΩ resistors
hold TXIDLEA/B pin at a mid level - don't connect this pin if the automatic idle detect function is desired.
This is the default state. Output in Idle if differential input signal less than value set by SD_TH pin.
Manual override, output in electrical Idle. Differential inputs are ignored.
TABLE 4. Receiver Electrical Idle Detect Threshold Adjust
SD_TH resistor value (Ω)
Receiver Electrical Idle Detect Threshold (DIFF p-p)
Float (no resistor required)
130 mV (default condition)
0
225 mV
80k
20 mV
SD_TH resistor value can be set from 0 through 80k ohms to achieve desired idle detect threshold, see Figure 5
Typical Performance Curves
30073093
FIGURE 5. Typical Idle Threshold vs. SD_TH resistor value
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30073095
FIGURE 6. Typical Power Dissipation (PD) vs. Output Differential Voltage (VOD)
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