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I am preparing a circuit using a TP4056. This circuit has a thermal pad. The datasheet says that this pad must be connected to ground or nothing.

However, some forum discussions talk about connecting it to GND or even VIN. Curious, I took apart a commercial module implementing a TP4056 and indeed the pad is connected to VIN. So I'm looking for the best truth. GND, VIN or nothing? Do you have this experience?

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  • \$\begingroup\$ Put a link to the forum topic or a screenshot of it. Also put a link to the datasheet that mentions thermal/exposed pad connection. \$\endgroup\$
    – Rohat Kılıç
    Commented Mar 20, 2023 at 8:22
  • \$\begingroup\$ I've browsed through several forums looking for information. I did not take the time to keep the links. I need your experience. Link to the data sheet: tp4056.com/d/tp4056.pdf \$\endgroup\$
    – hervema
    Commented Mar 20, 2023 at 8:42
  • \$\begingroup\$ It sounds like the pad is not internally connected to anything, so you can hook it up to either. But GND is your best option if you care about EMC issues. However, since it is a linear regulator it probably won't make that much difference in practice. The most important thing will be ensuring sufficiently low thermal resistance. \$\endgroup\$
    – Jon
    Commented Mar 20, 2023 at 9:35

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This is probably what you are talking about:

enter image description here

Quite possibly they mean "floating" by "impending", a bad translation (Impend means a form of hanging, if I'm not wrong).

The exposed pad appears to be electrically floating. This is the substrate that the chip is made on top of, and is not connected to to anything/anywhere chip-level. That's why the datasheet suggests it to be connected to GND, or left floating.

The voltage levels are low, so I don't think that the layer breaks down easily with voltages less than 20V. So it doesn't matter whether the pad is connected to GND or VIN. I don't know what could be the reason that it's connected to VIN in some designs, but it could be for easier layout.

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  • \$\begingroup\$ the key is probably "The exposed pad appears to be electrically floating"/"snd is not connected to to anything/anywhere chip-level", great for that. The module is able to manage 5V / 1A max. \$\endgroup\$
    – hervema
    Commented Mar 20, 2023 at 9:40
  • \$\begingroup\$ Also, what should be the pad thermal type to use for that ? I didn't see any info for that in datasheet. Same thread or another ? \$\endgroup\$
    – hervema
    Commented Mar 20, 2023 at 9:44
  • \$\begingroup\$ @hervema sorry, I couldn't understand your question. Do you mean thermal pad design on PCB? Or something else? \$\endgroup\$
    – Rohat Kılıç
    Commented Mar 20, 2023 at 10:11
  • \$\begingroup\$ sorry, yes I mean thermal pad design on PCB. \$\endgroup\$
    – hervema
    Commented Mar 20, 2023 at 10:18
  • \$\begingroup\$ @hervema thanks. The datasheet doesn't give any info about neither exposed pad design nor the SMD package's pad design. All you can do is to either 1) make as big as possible on the layer that the chip is mounted, and support it with vias to connect to another layer like shown here (no vias on EP) or 2) keep it at nominal size and use vias to connect to another big copper on another layer like shown here. \$\endgroup\$
    – Rohat Kılıç
    Commented Mar 20, 2023 at 10:32

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