DS50PCI402SQ Datasheet, PDF (8/38 Pages) Texas Instruments – DS50PCI402 2.5 Gbps / 5.0 Gbps 4 Lane PCI Express Repeater with Equalization and De-Emphasis

DS50PCI402
SNLS320H – APRIL 2010 – REVISED MARCH 2013
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TXIDLEA/B
0
Float
1
Table 6. 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 ensured.
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 7. 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.
250
V_DD = 2.5V
T_A = 25°C
200
150
100
50
0
0 10k 20k 30k 40k 50k 60k 70k 80k
SD_TH RESISTOR VALUE (:)
Figure 1. Typical Idle threshold vs SD_TH resistor value
Receiver Detection
The Rx detection process is a feature that can set the number of active channels on the DS50PCI402. By
sensing the presence of a valid PCIe load on the output, the channel can be automatically enabled for operation.
This allows the DS50PCI402 to configure inself to the proper lane width, whether it is a 4-lane, 2-lane, or 1-lane
PCIe link.
Automatic Rx Detection is enabled by a combination of PRSNT# and ENRXDET inputs. When these inputs are
set low, Automatic Rx Detection is enabled, cycling of the PRSNT# pin will reset the Rx detection circuitry,
initiating a new receiver detection sequence. Pulling the ENRXDET input to logic 1, allows for manual control of
the input termination.
The table below summarizes control pin and receiver detect operation for the DS50PCI402.
8
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