Redriver a Retimer for data transfer

18.10.2021 | F.A.Q.

Redrivers and Retimers have been used for years to extend the range of a wired signal. For a long time, it was Redrivers that dominated this space due to their relative simplicity and lower manufacturing and maintenance cost.

Depending on the complexity and data rate of the hardware design, Redrivers can be useful for smaller systems that operate at lower data rates.

For data rates above 16 Gbps, Redrivers do not have sufficient capabilities to compensate for significant signal degradation. PCIe 4.0 and 5.0 require the use of Retimers for compatibility. Other serial protocols, such as USB 4.0 and Thunderbolt 3.0, also have clearly defined Retimer requirements in their forward-looking specifications.

	Redriver	Retimer
Noise reduction	NONE	Resetuje cały szum wejściowy
Production and maintenance cost	low	High
Delay	~100ps	64ns based on PCIe 4 & 5
Equalizer	CTLE	CTLE, DFE i FIR
Debug mode	NONE	Eye diagram monitoring, link state status, receiver margining

The retimer resets the distorted signal caused by vibration, which it later regenerates into a clean signal ready for retransmission. The advantage of this is that there is no insertion loss, allowing the computing system and NVMe storage applications to take full advantage. Unfortunately, this is not fully achievable with Redriver. Any noise or random oscillation will be amplified along with the desired signal and in some cases Redriver itself can add messy noise to the output signal. It is also not possible to reset the noise for the input signal, as Retimer does

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Redriver a Retimer for data transfer

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