TO220

The TO-220 is a style of electronic component package, commonly used for transistors, silicon-controlled rectifiers, and integrated circuits. TO-220 packages commonly have three leads although units with two, four, five or seven leads are also manufactured. A notable characteristic is a metal tab with a hole, used in mounting the case to a heatsink. Components made in TO-220 packages can handle more power than those constructed in TO-92 cases.

Typical applications

TO-220 packages are heatsinkable, and thus can be used in projects where a large amount of power is being drawn. The top of the package has a metal tab with a hole used in mounting the component to a heatsink. Thermal compound is also used to provide greater heat transfer.

The metal tab is often connected electrically to the internal circuitry. This does not normally pose a problem when using isolated heatsinks, but an electrically-insulating pad or sheet may be required to electrically isolate the component from the heatsink if the heatsink is grounded or otherwise non-isolated. Many materials may be used to electrically isolate the TO-220 package, some of which have the added benefit of high thermal conductivity.

In applications where vertical clearance is at a premium (such as ISA cards in computers), it is often feasible to bend the leads at a right angle and mount the component flat to the printed wiring board using a screw and nut. This often provides enough surface area to heatsink the component when power dissipation is moderately high.

Advantages

*Can be used in high-power and high-current applications where equivalent components of other cases may be susceptible to damage.
*Grounding area makes handling easier by reducing the possibility of damage from electrostatic discharge.
*Mounting with the tab ensures the component to be held firmly in place.

Disadvantages

*More costly than equivalent components of other cases.
*Footprint requires considerably more surface area on a printed circuit board than other case styles. Heatsinks require even more board area.
*In the case of chassis-mounting, space must be dedicated to the components and/or their heatsinks, thereby increasing production costs.

Common components that use the TO-220 package

Common Voltage Regulators:
*7805, +5-volt regulated output
*7812, +12-volt regulated output
*LM317, voltage regulator
*LM317T, voltage regulator
*LM340, voltage regulator

Links

* [http://www.fairchildsemi.com/products/discrete/packaging/to220_2.html TO-220 3-pin Specification]