Other Parts Discussed in Thread: DS250DF210, DS250DF230, DS250DF410, DS250DF810,
Tool/software:
TI has several retimers in its 25/28G retimer product family. This FAQ breaks down some of the key differences between TI's 25/28G retimers.
| Part Number | Channel Count | CDR Lock Range [Gbps] | Minimum CTLE Boost |
| DS250DF210 | 2 |
20.6 - 25.8 10.3 - 12.9 5.15 - 6.45 |
8 dB at 12.89 GHz |
| DS250DF230 | 2 |
19.6 - 25.8 9.8 - 12.9 4.9 - 6.45 |
0 dB at 12.89 GHz |
| DS250DF410 | 4 |
20.2752 - 25.8 10.1376 - 12.9 5.0688 - 6.45 |
8 dB at 12.89 GHz |
| DS250DF810 | 8 |
20.2752 - 25.8 10.1376 - 12.9 5.0688 - 6.45 |
8 dB at 12.89 GHz |
| DS280DF810 | 8 |
20.2 - 28.4 10.1 - 14.2 5.05 - 7.1 |
8 dB at 14 GHz |
Channel Count:
Channel count is an important device characteristic to consider when implementing a retimer. TI offers 25/28G retimers with channel counts between 2 - 8 channels. For a front port application such as QSFP, TI often observes two topologies:
1) An 8 channel retimer is used for both ingress and egress
2) Two 4 channel retimers are used with one dedicated to ingress, and the other dedicated to egress.
Using a single device may reduce system cost.
Using multiple devices can offer more flexibility in the routing and can help optimize the signal conditioner placement.
CDR Lock Range:
All of the products in TI's 25/28G retimer family can lock to 25 GbE (25.78125 Gbps) and 10 GbE (10.3125 Gbps). However, beyond this, some products may be better for certain applications. For example, DS250DF230 better supports CPRI rates such as 9.8304 Gbps and 4.9152 Gbps.
Outside of the CDR lock range, these retimers can support rates through a CDR bypass signal chain. This signal chain only offers CTLE for signal conditioning, but can be sufficient for supporting lower data rates such as 1.25 Gbps (1 GbE).
Minimum CTLE Boost:
Most of TI's 25/28G retimers have a relatively high minimum CTLE boost. When designing in these retimers, it's important to add some insertion loss prior to the retimer receiver in order to avoid over-equalizing the signal. TI has observed that in most use cases, ensuring at least 3 dB of insertion loss prior to the DS2x0DFx10 retimer receiver allows for the retimer to offer good performance.