I'm planning to use the MCP1825 LDO regulator to be used with a 3.7V LiPo battery to power up a circuit with 3.3V requirement (microcontroller + ESP8266). However, I'm confused with which package to go with.

MCP1825 comes in a SOT223-3 and SOT223-5. The later offers two extra pins: Shutdown and Powergaurd. I'm not able to comprehend the datasheet as to why these two extra pins are provided.

Does it mean that once my battery voltage is below certain voltage (such as 2.7V), it will shutdown regulation and prevent over discharge? If yes, how do I set that limiting voltage? Should a SOT-233-3 package be sufficient to provide 3.3V regulated output?

Datasheet Link

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    \$\begingroup\$ Power Good not Guard. The first page in the datasheet explains it pretty well. \$\endgroup\$ – Mike Oct 8 '17 at 18:39
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    \$\begingroup\$ LiPo ranges from \$3.0\:\textrm{V}\$ when fully discharged to \$4.2\:\textrm{V}\$ when fully charged. The worst case dropout voltage of the MCP1825 is \$350\:\textrm{mV}\$. Given your \$3.3\:\textrm{V}\$ output, you will only be able to use your LiPo (with certainty) down to its own voltage of \$3.65\:\textrm{V}\$. Since that is close to the "nominal" voltage, I'm not sure how good your plans are. Also see: electronics.stackexchange.com/questions/38782/… \$\endgroup\$ – jonk Oct 8 '17 at 18:50
  • \$\begingroup\$ which gives the lowest thermal resistance, e.g. the best removal of heat? \$\endgroup\$ – analogsystemsrf Oct 8 '17 at 23:16

You need to add your own UVP protection for LiPo to drive enable signal.

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