MAX14950 Datasheet, PDF (15/17 Pages) Maxim Integrated Products – Quad PCI Express Equalizer/Redriver

MAX14950
Quad PCI Express Equalizer/Redriver
Detailed Description
The MAX14950 quad equalizer/redriver is designed
to support Gen III (8.0GT/s), Gen II (5.0GT/s), and
Gen I (2.5GT/s) PCIe data rates. The device contains
four identical drivers with electrical idle/receive detect
on each lane and equalization/deemphasis/preshoot
to compensate for circuit-board loss. Programmable
input equalization circuitry reduces deterministic jitter,
improving signal integrity. The device output features a
programmable output deemphasis/preshoot, permitting
optimal placement of key PCIe components and longer
runs of stripline, microstrip, or cable.
Programmable Input Equalization
Programmable input equalization is controlled by two
bits: INEQ1 and INEQ0 (Table 1).
Table 1. Input Equalization
INEQ1
0
0
1
1
INEQ0
0
1
0
1
INPUT EQUALIZATION (dB)
5
8
12
16
Programmable Output Deemphasis/
Preshoot
Programmable output deemphasis is controlled by three
bits: OEQ2, OEQ1, and OEQ0 for deemphasis/preshoot
ratios of 0dB, 3.5dB, 6dB, and 9dB (Table 2).
Table 2. Output Deemphasis/Preshoot
OEQ2 OEQ1 OEQ0
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
OUTPUT DEEMPHASIS/
PRESHOOT RATIO (dB)
0
3.5
6
6 (Peak-to-Peak Swing is 1.2V)
3.5
6
9 (Peak-to-Peak Swing is 0.9V)
9 (Peak-to-Peak Swing is 1.0V)
Receiver Detection
The device features receiver detection on each channel.
Upon initial power-up, if EN is high, receiver detection
initializes. Receiver detection can also be initiated on
a rising or falling edge of the RXDET input when EN is
high. During this time, the device remains in low-power
standby mode and the outputs are disabled, despite the
logic-high state of EN. Until a channel has detected a
receiver, the receiver detection repeats indefinitely on
each channel. If a channel detects a receiver, the other
channels are limited to retries for 100ms (typ). For each
channel upon receiver detection, input common-mode
termination and electrical idle detection are enabled
(Table 3).
Electrical Idle Detection
The device features electrical idle detection to prevent
unwanted noise from being redriven at the output. When
the device detects that the differential input has fallen
below the VTX-IDLE-THRESH low limit, it squelches the
output. For differential input signals that are above VTX-
IDLE-THRESH high limit, the device turns on the output
and redrives the signal. There is little variation in output
common-mode voltage between electrical idle and
redrive modes.
Table 3. Receiver Detection Input Function
RXDET
X
EN
DESCRIPTION
0 Receiver detection is inactive.
Following a rising edge of EN sig-
nal, indefinite retry until receiver
X
1 detects at least one channel.
Retries stop after 100ms (typ) if
any channel receiver is detected.
Rising/Falling
Edge
1
Initiates receiver detection.
X = Don’t care.
Maxim Integrated
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