Stratix® V Device Handbook: Volume 1: Device Interfaces and Integration

ID 683665
Date 10/18/2023
Public
Document Table of Contents

6.2.3.1. Guideline: Using DPA-Enabled Differential Channels

Each differential receiver in an I/O block has a dedicated DPA circuit to align the phase of the clock to the data phase of its associated channel. If you enable a DPA channel in a bank, you can use both single-ended I/Os and differential I/O standards in the bank.

You can place double data rate I/O (DDIO) output pins within I/O modules that have the same pad group number as a SERDES differential channel. However, you cannot place SDR I/O output pins within I/O modules that have the same pad group number as a receiver SERDES differential channel. You must implement the input register within the FPGA fabric logic.

The following figure illustrates the clock network for DPA and SERDES resources in Stratix V devices.

Figure 118. LVDS and DPA Clock Network

If you use DPA-enabled channels in differential banks, adhere to the following guidelines.

Using Center and Corner PLLs

If two PLLs drive the DPA-enabled channels in a bank—the corner and center PLL drive one group each—there must be at least one row (one differential channel) of separation between the two groups of DPA-enabled channels, as shown in the following figure.

Figure 119. Center and Corner PLLs Driving DPA-enabled Differential I/Os in the Same Bank

This separation prevents noise mixing because the two groups can operate at independent frequencies. No separation is necessary if a single PLL is driving both the DPA-enabled channels and DPA-disabled channels.

Using Both Center PLLs

You can use center PLLs to drive DPA-enabled channels simultaneously, if they drive these channels in their adjacent banks only, as shown in the previous figure. The center PLLs cannot drive cross-banks simultaneously. Refer to the following figures.

Figure 120. Center PLLs Driving DPA-enabled Differential I/Os
Figure 121. Invalid Placement of DPA-enabled Differential I/Os Driven by Both Center PLLs

Using Both Corner PLLs

You can use the left and right corner PLLs to drive DPA-enabled channels simultaneously, if they drive the channels in their adjacent banks only. There must be at least one row of separation between the two groups of DPA-enabled channels.

There are two PLL in each corner of the device. However, only one corner PLL can be use to drive DPA-enabled channels in a quadrant.

Figure 122. Invalid Usage of Corner PLLs Driving DPA-enabled Differential I/Os

DPA Restrictions

Because there is only a single DPA clock bus, a PLL drives a continuous series of DPA channels.

To prevent noise mixing, use one row of separation between two groups of DPA channels.