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I plan on using this 3.3v regulator

It has 4 pins on the SOT-223 package

I plan on doing the following ( but want to check )

  • Pin 1 - Gnd
  • Pin 2 - Vout - 3.3v -- Tied to pin 4 feeding my circuit
  • Pin 3 - Vin - 5v Supply
  • Pin 4 - Vout - 3.3v -- Tied to pin 2 feeding my circuit

Does this look correct?

The reason I act is that pin 4 is a bit 'odd'. This question has set me straight : LDO - SOT223 - What's the Fourth pin for?

Basically its a tab for heatsinking, but it is typically connected to Pin 2.

Can I therefore safely just have a pad for the Tab(pin 4) with nothing connected to it? And use pin 2 for the vOUT alone?

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  • \$\begingroup\$ Use an ohmmeter and check for continuity. \$\endgroup\$ – StainlessSteelRat Jul 1 at 18:39
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Often, pin 2 is not brought out to a pin you can solder to the board. Thus pin 4 is used. The datasheet covers both options. See the TO-252 or DPAK. I use those when higher current is involved to increase the cooling area available. There pin 2 is still connected to the tab, but does not go down to the board for soldering.

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It is literally on page 3 of the datasheet, which you linked in the question.

enter image description here

Where exactly is the confusion? It states very clearly that Adj/GND in the SOT-223 is pin 1. Vin pin 3, and Vout is pins 2 and 4.

There should be no need to double check if you read this table. Remember the input and output capacitors.

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  • \$\begingroup\$ I want to make sure my understand is right, and that i can join together pins 2 & 4? \$\endgroup\$ – RenegadeAndy Jul 1 at 17:53
  • \$\begingroup\$ See my updated question above \$\endgroup\$ – RenegadeAndy Jul 1 at 18:08
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    \$\begingroup\$ The datasheet and this answer are very clear. I wonder who downvoted this answer. +1 to compensate. Moreover at addresses the missing capacitors in OP's textual schematic. \$\endgroup\$ – Huisman Jul 1 at 18:12
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    \$\begingroup\$ @RenegadeAndy Your updated question and I believe this answer still gives you the same answer. I don't think it was necessary to downvote this answer. If you're still confused on how to configure the pins, I recommend looking at some application notes for the datasheet. Just tie them together on the schematics. It's not like it will affect the way your system performs. \$\endgroup\$ – KingDuken Jul 1 at 18:17
  • \$\begingroup\$ Hmm could the 2 downvoters explain why they thought this answer is wrong? From what I can see, it is very clearly correct. Even with the updated question, the answer still stands. \$\endgroup\$ – MCG Jul 1 at 19:50

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