DS50PCI402EVK/NOPB National Semiconductor, DS50PCI402EVK/NOPB Datasheet - Page 9

• Manufacturer Part Number: DS50PCI402EVK/NOPB
• Description: BOARD EVALUATION DS50PCI402
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of DS50PCI402EVK/NOPB

• Main Purpose: Interface, Transceiver, PCI Express
• Embedded: No
• Utilized Ic / Part: DS50PCI402
• Primary Attributes: 5 Gbps Quad Lane Bidirectional Buffer & Equalizer
• Secondary Attributes: 3.3V LVCMOS Input Tolerant for SMBus Interface
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: DS50PC1402EVK/NOPB

Receiver Detection
The Rx detection process is a feature that can set the number
of active channels on the DS50PCI402. By sensing the pres-
ence of a valid PCIe load on the output, the channel can be
automatically enabled for operation. This allows the DS50P-
CI402 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
RX Detect: Range of Operation
The Rx detection process used in the DS50PCI402 is de-
signed to be fully compliant with the PCIe 2.0 base specifica-
tion. The receiver detection circuitry will accurately detect a
receiver when both conditions listed below are true:
•
•
PRSNT#
DS50PCI402 within Recommended Operating Range for
Temperature and Supply Voltage
For receiver Z
0
0
0
0
1
ENRXDET RXDETA/B
RX-DC
X
0
0
1
1
= 40 (min) to 60 (max) Ohms
TABLE 7. Receiver Detect Pins for A and B ports (LVCMOS inputs)
0
1
0
1
X
>50KΩ to VDD
>50KΩ to VDD
>50KΩ to VDD
>50KΩ to VDD
Termination
Input
50Ω
50Ω
50Ω
Termination sensed on
9
PCIe Input
PCIe Input
Output
Hi - Z
Hi - Z
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 in-
put to logic 1, allows for manual control of the input termina-
tion.
The table below summarizes control pin and receiver detect
operation for the DS50PCI402.
Note: To ensure robust system operation, the DS50PCI402
will only signal a valid receiver detection if both halves of the
differential output pair detect a proper 40 - 60 Ohm receiver
impedance. If the receiver detection circuitry senses a load
impedance greater than Z
pair, it will be interpreted as no termination load present (i.e.
the corresponding DS50PCI402 input termination will remain
High-Z).
X
X
X
Automatic RXDET: Rx detection state
machine enabled. Outputs will test for the
presence of a receiver input every 12 msec
until detection occurs. Input termination
remains >50KΩ to VDD until receiver is
detected. Once receiver is detected, input
impedance to VDD is 50Ω.
Automatic RXDET: Rx detection state
machine enabled. Outputs will test for the
presence of a receiver input every 12 msec
for 600 msec and then stop. Input
termination remains >50KΩ to VDD until
receiver is detected. Once receiver is
detected, input impedance to VDD is 50Ω.
Restart detection if RXDETA/B is pulsed
low-high.
Manual RXDET: Rx detection state machine
disabled. Input termination >50KΩ.
Associated output channels in low power
idle mode.
Manual RXDET: Rx detection state machine
disabled. Input termination 50Ω. Associated
output channels set to active.
Power down mode: Input termination
>50KΩ. Associated output channels off. Part
in power saving mode. PRSNT# should be
held high for a minimum of 5 us to ensure
complete analog power down. The
Automatic RXDET functionality will be re-
initialized on the falling edge of PRSNT#.
RX-DC
on either trace of a differential
Function
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