The CTLE boosts the signal that is attenuated due to channel characteristics. Each receiver buffer has independently programmable equalization circuits. These equalization circuits amplify the high-frequency component of the incoming signal by compensating for the low-pass characteristics of the physical medium. The CTLE can support both DC and AC gain.
DC gain circuitry provides an equal amplification to the incoming signal across the low frequency spectrum. AC gain circuitry provides amplification to the high-frequency spectrum gain of the incoming signal.
Arria® 10 transceivers support dual mode CTLE.
High Gain Mode
High gain mode supports data rate up to 17.4 Gbps. This mode provides both AC and DC gain. There are two bandwidth settings available for this mode.
- Full Bandwidth—This mode has a peaking frequency of 6.25 GHz offering AC gain at 17 dB.
- Medium Bandwidth—This mode has a peaking frequency of 3.125 GHz offering AC gain at 21 dB.
High Data Rate Mode
High Data Rate Mode is a low power mode that supports data rates up to 25.8 Gbps. It is the default mode if none of the modes are selected in the Intel® Quartus® Prime Assignment Editor or Intel® Quartus® Prime Settings File (.qsf). This mode provides an alternative path for high gain mode. High Data Rate Mode can be used to compensate for the loss similar to CEI 28G VSR. High data rate mode supports four bandwidth modes: Full, three-fourths, one-half, and one-fourth bandwidth modes. Full bandwidth mode can provide AC peaking at approximately 8 dB at a peaking frequency of 14 GHz. High data rate mode can be operated in three-fourths, one-half, and one-fourth bandwidth with 9 GHz, 5 GHz, and 2.5 GHz peaking frequencies. In high data rate mode, AC gain values and DC gain values cannot be controlled individually as done in high gain mode. The recommended AC gain values in high data rate mode include the appropriate setting of DC gain to get the required peaking at respective peaking frequencies.
CTLE can only be supported in manual mode with the exception of PCIe Gen3, which supports triggered mode. CTLE mode and CTLE gain can be set through Intel® Quartus® Prime Assignment Editor or Intel® Quartus® Prime Settings File and Avalon® memory-mapped interface registers.
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