Stratix V Device Handbook: Volume 2: Transceivers

ID 683779
Date 11/23/2021
Public
Document Table of Contents

2.2.2.2.5. Bonded Channel Configurations Using the PLL Feedback Compensation Path

You can bond channels across multiple banks by using the PLL feedback compensation path.

The PLL feedback compensation path loops the parallel clock, which is used by the PCS blocks, back to the transmitter PLL. The PLL feedback compensation path synchronizes the parallel clock used to clock the PCS blocks in all transceiver banks with the refclk. You can use the PLL feedback compensation path to reduce channel-to-channel skew, which is introduced by the clock divider in each transceiver bank.

To bond channels using the PLL feedback compensation path, the input reference clock frequency used by the transmitter PLL must be the same as the parallel clock that clocks the PCS of the same channel. If the input reference clock frequency is not equal to the parallel clock frequency, use a fractional PLL to synthesize an input reference clock with the same frequency as the parallel clock.

Notes:

  • fPLL does not support PLL feedback compensation when used as a TX PLL.
  • Every transceiver bank with a bonded channel configured using the PLL feedback compensation path consumes a transmit PLL.
Figure 62. Three Transceiver Bank Channels Bonded Using the PLL Feedback Compensation PathThe figure shows 18 transmitter channels within three transceiver banks that are bonded using the PLL feedback compensation path. A fractional PLL is used to synthesize a clock that has the same frequency as the parallel clocks, which are looped back to the transmitter PLL.


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