![]() However the 78xx series covers a number of different voltage ranges 7805, 7812 and so on, all in the same package. The 7909 is a negative 9 volt regulator and the 7809 is a positive 9 volt regulator. The photograph to the far upper left shows two voltage regulators, a 7909 and a 7809 regulator, both mounted to a printed wiring board. The dimensions table for the TO220 package also provides a pin-out example of a FET, but the terminals could just as well identify the leads of a transistor. Note that part of the TO-220 body may lift off the mounting surface as pressure is applied to the tab by the mounting bolt, use conductive epoxy to secure the body of the TO-220 to the mounting surface, normally the printed wiring board. The surface mount version of a TO-220 is the TO-263. In some cases the tab is just used as a heat sink. However not all styles of the TO-220 package use the tab as an electrical pin. ![]() ![]() The bottom tab may be electrically connected to the Drain or Collector. Note the location of the Thermal Pad in the picture above. As does the location of the thermocouple, under the die, next to the die, or on the tab. Which ever mounting method is used will result in two completely different values in thermal impedance. Heat dissipation is handled by the metal tab however during thermal measurements the case might be restrained with a metal clip holding the plastic body or a screw through the metal tab. The JEDEC specification will define the location of the thermocouple on the case. Case temperature is that temperature measured at a specified point on the case of a ![]() Note that the graphic to the left has a copper pad on the PWB but does not attach the tab to the board.Ĭase temperature. When attached to a PWB, a copper pad should be located underneath the thermal tab of the TO-220. Other factors that may effect the mounting include using a Mica washer, copper washer, and thermal grease to aid in heat transfer. In this case the TO-220 uses a metal tab, and a major portion of the rear of the device is also metal however other packages may be completely metal and use the term case mount. Semiconductor device to a to achieve thermal management of the case temperature. Is a style of package which provides a method of readily attaching one surface of the ![]()
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