SOT-223 Component Package

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Date Published:	January 8, 2015
Last Modified:	April 19, 2024

Overview

SOT-223 is a family of SMD component packages commonly used for medium-power discrete semiconductor components and basic ICs such as linear regulators. It is characterised by standard gull-wing pins on one side of the body and a larger tab on the other side.

There are three main variants in the SOT-223 family:

SOT-223-3 (3 pin excl. tab)
SOT-223-4 (4 pin excl. tab)
SOT-223-5 (5 pin excl. tab)

Members of the SOT-223 family are used for things such as MOSFETs, load switches, high-power linear regulators and current sources.

Conflicting Naming Conventions

WARNING

Some manufacturers use the term SOT-223-3 to refer to the 3-pin, 1-tab package, while others count the tab as a “pin”, and so name it SOT-223-4. However this conflicts with the first lot of manufacturers who use the term SOT-223-4 to refer to the package with 4 pins and 1 tab. In summary, BE CAREFUL.

This page associates the x in SOT-223-x to stand for the number of pins excluding the tab. This is the most popular convention.

SOT-223-3

The SOT-223-3 (TO-261AA) component package is the most common variant within the SOT-223 family. It looks similar to the SOT-23 package, but with a tab on one side instead of legs.

It is commonly used for medium-power linear regulators and load switches.

The tab is sometimes electrically connected to pin 2 (the middle pin on the other side of the package), or sometimes electrically isolated for all other pins and called pin 4. For example, the AZ1117I linear regulator from Diodes Incorporated connects the tab to pin 2:

The pin diagram for the AZ1117I in a SOT-223 package. Note how the tab is connected to pin 2.

Synonyms

DCY: Texas Instruments¹.
KC-3: Analog Devices’ name².
MP04A: National Semiconductor’s drawing number³.
PG-SOT-223-4: Infineon’s name⁴.
R-PDSO-G4: Texas Instruments¹.
TO-261-4: JEDEC name⁵.
TO-261AA: JEDEC name⁵ ².

Thermal Resistance

Texas Instruments gives the following thermal resistance data for the SOT-223-3 package (taken from http://www.ti.com/lit/ds/symlink/tps7b6933-q1.pdf, as of Dec 2017, URL is unavailable).

Property	Symbol	Value
Junction-to-ambient thermal resistance	\(R_{\theta JA}\)	\(64.2^{\circ}C/W\)
Junction-to-case (top) thermal resistance	\(R_{\theta JC(top)}\)	\(46.8^{\circ}C/W\)
Junction-to-board thermal resistance	\(R_{\theta JB}\)	\(13.3^{\circ}C/W\)
Junction-to-top characterisation parameter	\(R_{\psi JT}\)	\(6.3^{\circ}C/W\)
Junction-to-board characterisation parameter	\(R_{\psi JB}\)	\(13.2^{\circ}C/W\)

All of the parameters in the above table were measured with the SOT-223-3 package soldered to a JEDEC standard high-K profile, JESD 51-7, 2s2p four layer board with 2-oz copper. The copper pad was soldered to the thermal land pattern.

The thermal resistance of the TO-261AA (SOT-223-3) component package for various PCB footprints.

Standard Linear Regulator Pinout

The SOT-223-3 package is commonly used for small, medium-power linear regulators. There is a de-facto standard pinout that many manufacturers use when incorporating a linear regulator into the SOT-223-3 package:

The de-facto standard pinout for a linear regulator inside a SOT-223-3 package. This image also shows the standard PCB footprint used to achieve a low thermal resistance. Image from http://www.ti.com/.

Standard Load Switch Pinout

The SOT-223-3 package is commonly used for smaller low and high-side load switches. As such, there is a de-facto standard pinout that many manufacturers use for load switches in the SOT-223-3 package: