Stratix V Device Handbook: Volume 2: Transceivers

ID 683779
Date 11/23/2021
Document Table of Contents Continuous Time Linear Equalization (CTLE)

Each receiver buffer has five independently programmable equalization circuits that boost the high-frequency gain of the incoming signal, thereby compensating for the low-pass characteristics of the physical medium. For Stratix V GX channels, the equalization circuitry provides up to 16 dB of high-frequency boost. For Stratix V GT channels, the equalization circuitry provides up to 15 dB of high-frequency boost. The CTLE operates in two modes: manual mode and adaptive equalization (AEQ) mode.

You can dynamically switch between these modes.

Note: The CTLE cannot be bypassed.

Manual Mode

Manual mode allows you to manually adjust the continuous time linear equalization to improve signal integrity. You can statically set the equalizer settings in the IP or you can dynamically change the equalizer settings with the reconfiguration controller IP.

Adaptive Equalization Mode

AEQ mode eliminates the need for manual tuning by enabling the Stratix V device to automatically tune the receiver equalization settings based on the frequency content of the incoming signal and comparing that with internally generated reference signals. The AEQ block resides within the PMA of the receiver channel and is available on all GX channels.

Note: AEQ mode is not supported in GT channels.

There are two AEQ modes: one-time and powerdown:

  • One-time mode—The AEQ finds a stable setting of the receiver equalizer and locks to that value. After the stable setting is locked, the equalizer values do not change.
  • Powerdown mode—The AEQ of the specific channel is placed in standby mode and the CTLE uses the manually set value.