Multi-leaded power package

The multi-leaded power package is a style of electronic component package, commonly used for high power integrated circuits, especially for monolithic audio amplifiers. It was derived from single in-line package. The difference is the lead arrangement; multi-leaded power packages usually have the lead bent to zig-zag pattern. Multi-leaded power packages commonly have more than three leads; nine-, thirteen- and fifteen-lead units are common, units with five or seven leads with TO-220 style are also manufactured. A notable characteristic is a metal tab with a hole, used in mounting the case to a heatsink. The physical view of multi-leaded power packages are simply stretched TO-220 packages. Components made in multi-leaded power packages can handle more power than those constructed in TO-220 cases, or even TO3 cases with thermal resistance no less than 1.5 C/W.^[1]

One well-known STMicroelectronics brand of this type of package is Multiwatt.^[2]

Typical applications

Multi-leaded power 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; ground and supply connections are common. 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. The material used to electrically isolate the multi-leaded power package, like mica, needs to have a 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.

References

^ Hopkins, T.; Tiziani, R. (1989), "Transient thermal impedance considerations in power semiconductor applications", Automotive Power Electronics 1989, Dearborn, MI, USA, USA: IEEE, pp. 89–97, doi:10.1109/APE.1989.97162, S2CID 111154062
^ Hopkins, T.; Cognetti, C.; Tiziani, R. (1988). "AN261 Designing with Thermal Impedance" (PDF). STMicroelectronics. Archived (PDF) from the original on 2017-12-23.

[APE1989-1] Hopkins, T.; Tiziani, R. (1989), "Transient thermal impedance considerations in power semiconductor applications", Automotive Power Electronics 1989, Dearborn, MI, USA, USA: IEEE, pp. 89–97, doi:10.1109/APE.1989.97162, S2CID 111154062

[ST-AN261-2] Hopkins, T.; Cognetti, C.; Tiziani, R. (1988). "AN261 Designing with Thermal Impedance" (PDF). STMicroelectronics. Archived (PDF) from the original on 2017-12-23.

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