DS125DF1610 Datasheet, PDF (15/81 Pages) Texas Instruments – 9.8 to 12.5 Gbps 16-Channel Retimer

www.ti.com
DS125DF1610
SNLS482A – APRIL 2014 – REVISED DECEMBER 2015
Feature Description (continued)
The CTLE consists of 4 stages, with each stage having 2-bit boost control. This allows for 256 different stage-
boost combinations. The CTLE adaption algorithm allows the CTLE to adapt through 32 of these stage-boost
combinations. These 32 stage-boost combinations comprise the EQ Table in the channel registers; see channel
registers 0x40 through 0x5F. This EQ Table can be reprogrammed to support up to 32 of the 256 stage-boost
settings. Users also have the option of limiting the EQ table length to any value between a minimum value of 1
and a maximum value of 32.
CTLE boost levels are determined by summing the boosts levels of the 4 stages. Different stage-boost
combinations that sum to the same number will have approximately the same boost level, but will result in a
different shape for the EQ transfer function (boost curve). The boost levels can be set between 0 dB and 31 dB.
The CTLE bandwidth can be adjusted through SMBus control to 3 different levels:
Table 1. CTLE Bandwidth Settings
CTLE BANDWIDTH SETTING
Full Rate (default)
Mid Rate
Half Rate
BANDWDITH (GHz) (TYP)
9
7
5
The fourth stage in the CTLE can be programmed through the SMBus interface to become a limiting stage rather
than a linear stage. This is useful in some applications, but it should not be typically used in combination with the
DFE.
7.3.4 Cross Point Switch
Each quad has a 4x4 non-blocking analog cross point switch. This allows for full switching or broadcasting of
data between any input within the quad to any output within the quad. Since the cross point switch is an analog
implementation, all of the channels are allowed to operate asynchronously. The analog implementation also
minimizes added latency through the device.
As shown in Figure 3, the cross point switch connections for each quad are located between CTLE and DFE in
each channel.
The cross point switch consists of 4 sets of MUXs and buffers. In each channel there is a local buffer and a multi-
drive buffer. The local buffer transmits data from the CTLE to the DFE of the same channel. The multi drive
buffer transmits data from the CTLE to the DFE(s) of other channels within the quad. Each channel has two
MUXs:
1. Data path mux – Selects whether to get data from the local buffer or from the other channel’s multi-driver
buffer
2. Control bus mux – Selects where the signal detect and EQ control bus should be connected. This setting
should mirror the data path mux setting. Note, when an EQ is connected to another channel’s CDR the EQ
becomes associated with that CDR’s register set. For example, if the cross point was configured to do point
to point switching from the inputs of channel 0 to the output of channel 1 and the inputs of channel 1 to the
outputs of channel 0, the EQ physically located at the pins for inputs of channel 0 would be accessible
through the register set of channel 1.
A simplified diagram of the cross point switch is shown in Figure 3.
Copyright © 2014–2015, Texas Instruments Incorporated
Product Folder Links: DS125DF1610
Submit Documentation Feedback
15