AN 958: Board Design Guidelines

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ID 683073
Date 1/28/2022
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5.1.5.4.7. On-Chip Termination

Stratix® family of devices has on-chip resistors designed to support termination for several I/O standards. On-chip resistors simplify the task of board design by freeing board space and offering more freedom in signal routing. Also, using the on-chip resistors reduces stub reflection. Consequently, Stratix® series devices provides better load and/or source termination, which leads to better signal integrity.

All transceivers in Stratix® series devices have programmable, per channel internal termination resistors, which can be programmed to be either 50-, 60-, or 75-Ω single-ended resistors. In differential mode, the resistors generate 100-, 120-, or 150-Ω termination. Figure 42 and Figure 43 show receiver and transmitter on-chip termination schemes. Because different I/O standards require different termination resistors, programmable internal termination resistors can be helpful. For example, XAUI and Infiniband applications require 100-Ω differential termination, while Gigabit Ethernet and Fibre Channel require 150-Ω differential termination.

Figure 42. Receiver On-Chip Termination

You can bypass the on-chip resistors used in the receiver and use external resistors.

Figure 43. Transmit On-Chip Termination

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