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  • TI Thinks Resolved

Does the LM7915CT have an insulated backing?

This LM7915CT 15 volt regulator IC, which I have not yet ordered, comes in a TO-220 case. I need to know if the back of the case is metallic or epoxy. The reason it's important is that this part will be mounted to the chassis ground and if it's metallic and if it's consistent with every other TO-220 case I've come to know, then the center pin (pin 2) will be electrically  connected to the metal case. That is not acceptable because pin 2 is the voltage input. The datasheet does not indicate whether or not it's insulated. Thank you for your help.

  • Hi David,

    Figure 1 of the LM79 datasheet shows the tab is electrically connected to the voltage input. If you need to connect the tab to chassis ground for heat sinking, you can use an electrically insulated thermal pad and insulated bushing/shoulder washer with a metal screw and nut. This will provide a thermal path and prevent shorting of voltage input to chassis ground. Thermal pad or interface material generally provides a better thermal path than direct metal to metal contact.

    www.ti.com/.../lm79.pdf
    www.ti.com/.../mmsf014.pdf

    Best,
    Eric Preiss | Applications and Validation Engineer | Linear and Low Dropout Regulators | Texas Instruments

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