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?

  • \$\begingroup\$ Use an ohmmeter and check for continuity. \$\endgroup\$ – StainlessSteelRat Jul 1 '19 at 18:39

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.


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.

  • \$\begingroup\$ I want to make sure my understand is right, and that i can join together pins 2 & 4? \$\endgroup\$ – RenegadeAndy Jul 1 '19 at 17:53
  • \$\begingroup\$ See my updated question above \$\endgroup\$ – RenegadeAndy Jul 1 '19 at 18:08
  • 1
    \$\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 '19 at 18:12
  • 1
    \$\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 '19 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 '19 at 19:50

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.