I experiment with the PIC24 series of μCs fairly often and have noticed that I can run them successfully from a 3.7v LiPo battery pack without a regulator. The batteries charge to around 4.2v fully charged and down to a little below 3.7v drained. This is only slightly above the suggested 3.3v. I just wondered if there are any side-effects of this? Does it affect the internal oscillators or some other internal processes? Or is the effect negligible?

  • \$\begingroup\$ You can use low voltage drop linear regulator. Ex: MCP1702 \$\endgroup\$ – Triak Oct 16 '15 at 22:42
  • \$\begingroup\$ I realize I can use an LDO regulator, but I'm more specifically wondering what are the effects of not using a regulator to bring the supply into the datasheet given range of 2-3.6v. \$\endgroup\$ – Jacob Calvert Oct 16 '15 at 22:44
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    \$\begingroup\$ @JacobCalvert With 4.2V you are abusing an absolute maximum rating. Microcontroller can malfunction in any way (temporary or permanent, overt or latent). Read the absolute max ratings in the datasheet, and don't abuse them. Got it? \$\endgroup\$ – Nick Alexeev Oct 16 '15 at 22:47
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    \$\begingroup\$ The same long-term effects as overvolting/overclocking a CPU. Probably more electromigration and less life. Also look up EOS (electrical overstress); there are some nice inside pictures of devices damaged. \$\endgroup\$ – Fizz Oct 16 '15 at 22:58
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    \$\begingroup\$ If you don't use it within the specifications it may or may not work to the listed specifications. This may or may not be obvious (e.g. total refusal to work vs. the ADC disliking Thursday evenings). It may or may not do this for the expected lifetime. But at least you'll know why when it finally breaks. \$\endgroup\$ – David Oct 16 '15 at 23:09

The datasheet warns:

Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device.

But can you use a voltage above 3.6 V, but still below the absolute maximum ratings?

This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operation listings of this specification is not implied.

No; it's still not guaranteed to work.

But does this at least avoid the "permanent damage" mentioned above?

Exposure to Absolute Maximum Rating conditions for extended periods may affect device reliability.

No; you still can damage your device, it will just not happen immediately.

But what will actually happen? This is impossible to predict exactly; any part of the µC might fail, fully or partially.


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