MAX14955 Datasheet, PDF (16/19 Pages) Maxim Integrated Products – Computer on Modules

MAX14955
Functional Diagram
Single-Lane PCIe Gen III Redriver
with Equalization and Extended
Temperature Operation
INEQ_0
INEQ_1
IN_P
IN_M
EN RXDET
OEQ_2
RECEIVER DETECT
MANAGER
OUTPUT
ENABLE
OUT_P
OUT_M
RHI
ELECTRICAL IDLE
DETECTOR
MAX14955
Detailed Description
The MAX14955 dual equalizer/redriver supports Gen
III (8GT/s), Gen II (5GT/s), and Gen I (2.5GT/s) PCIe
data rates. The device contains two identical drivers
with 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
features 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 for channel A is con-
trolled by two bits: INEQA1 and INEQA0 and for channel
B is controlled by two bits: INEQB1 and INEQB0 (Table 1.)
Programmable Output Deemphasis
Programmable output deemphasis/preshoot for channel A
is controlled by the three bits: OEQA2, OEQA1, OEQA0
and channel B is controlled by the three bits: OEQB2,
OEQB1, OEQB0 (Table 2.)
OEQ_0
OEQ_1
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 part remains in low-power standby
mode and the outputs are squelched, despite the logic-
high state of EN. Until a channel has detected a receiver,
the receiver detection repeats indefinitely on each chan-
nel. If a channel detects a receiver, the other channel is
limited to a few retries. Upon receiver detection, input
common-mode termination and electrical idle detection
are enabled (Table 3.)
Table 1. Input Equalization
INEQ_1
0
0
1
1
INEQ_0
0
1
0
1
INPUT EQUALIZATION (dB)
5
8
12
16
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