DS125RT410 Datasheet, PDF (11/42 Pages) Texas Instruments – DS125RT410 Low Power Multi-Rate Quad Channel Retimer

DS125RT410
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DEVICE CONFIGURATION
SNLS459 – APRIL 2011
The DS125RT410 can be configured by the user to optimize its operation. The four channels can be optimized
independently in SMBus master or SMBus slave mode. The operational settings available for user configuration
include the following.
• CTLE boost setting
• Rate and subrate setting
• Driver output voltage
• Driver output de-emphasis
• Driver output rise/fall time
CTLE Boost Setting
The CTLE is a four-stage amplifier with an adjustable, quasi-high-pass transfer function on each stage. The
overall frequency response of the CTLE is set by adjusting the boost of each stage independently. Each stage of
the CTLE can be set to one of four boost settings. The amount of high-frequency boost supplied by each stage
generally increases with increasing boost settings.
The CTLE can also be configured to adapt automatically to provide the optimum boost level for its input signal.
Automatic adaptation of the CTLE only is the default mode of operation for the DS125RT410.
Rate and Subrate Setting
Register 0x2f, bits 7:4, Registers 0x60, 0x61, 0x62, 0x63, and 0x64
The DS125RT410 is part of a family of retimer devices differentiated by different VCO frequency ranges. Each
device in the retimer family is designed for operation in specific frequency bands and with specific data rate
standards.
The DS125RT410 is designed to lock rapidly to any valid signal present at its inputs. It is also designed to detect
incorrect lock conditions which can arise when the input data signals are strongly periodic. This condition is
referred to as “false lock”. The DS125RT410 discriminates against false lock by using its 25 MHz reference to
ensure that the VCO frequency resulting from its internal phase-locking process is correct.
To determine the correct VCO frequency, the digital circuitry in the DS125RT410 requires some user-supplied
information about the expected data rate or data rates. This information is provided by writing several device
register using the SMBus.
Standards-Based Modes
The DS125RT410 is designed to automatically operate with various multi-band data standards.
The first set of register writes constrain the coarse VCO tuning and the VCO divider ratios. When these registers
are set as indicated in Table 1, the DS125RT410 restricts its coarse VCO tuning to a set of coarse tuning values.
It also restricts the VCO divider ratio to the set of divider ratios required to cover the frequency bands for the
desired data rate standard. This enables the DS125RT410 to acquire phase lock more quickly than would be
possible if the coarse tuning range were unrestricted.
Standards
CPRI1
CPRI2
PROP3
Interlaken1
Interlaken2
Ethernet
Table 1. Rate and Subrate Values versus Standards and Data Rates
Data Rates (Gb/s)
VCO Frequencies (GHz)
2.4576, 4.9152, 9.8304 9.8304
3.072, 6.144
12.288
6.25
12.5
3.125, 6.25
12.5
10.3125
10.3125
1.25, 10.3125
10.0, 10.3125
Divider Ratios
1, 2, 4
2, 4
2
2, 4
1
1, 8
Register 0x2F Value (hex)
0x34
0x44
0xA4
0xB4
0xC4
0xF4
Copyright © 2011, Texas Instruments Incorporated
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