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AR# 12632

Signal Integrity and the PCB - Can outputs be tied together to increase drive strength?

Description

If a higher drive current is required than can be supplied by a single output pin, can multiple outputs be tied together? Are there any issues to be aware of when doing this?

Solution

Generally, this method is successful; however, skew between pins that are tied together should be minimized. If not, contention between the pins could lead to large transient currents, but will not cause damage to the device. To minimize skew, outputs that are tied together should have low output skew, and output (IOB) registers should be used.

The number of pins that can be tied together is dictated by the effect of SSOs (simultaneous switching outputs), which can lead to ground bounce. Though skew between pins can be minimized, there might still be transient currents, which will effectively reduce the number of SSOs that can be tolerated before ground bounce becomes an issue.

AR# 12632
Date Created 08/29/2007
Last Updated 12/15/2012
Status Active
Type General Article