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I'm curious as to why the following image of a MCP1827S-3302E/EB voltage regulator, which has three legs shows up with 4 legs in EagleCAD.

Voltage Regulator Symbol

I noticed that there are two ground pins, GND and GND_2 in the schematic, why is this?

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up vote 6 down vote accepted

One of the ground pins on the schematic symbol represents the exposed pad on the device package, which should be connected to ground on the PCB.

The exposed pad is visible at the rear side in the image below:

enter image description here

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It's worth mentioning that this is no longer necessary in Eagle 6, they made it possible to assign one schematic pin to multiple pads on the physical package. This was not previously the case. – Joe Baker Jan 10 '13 at 16:24

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