Circuitry connecting to battery, regulation circuit and method thereof

A method for operating a circuitry, comprising:

• providing a regulation circuit comprising a first node, a second node and a third node, wherein the first node electrically connects to a power source, and the second node electrically connects to a cathode of a battery;
• providing a first transistor set, electrically connecting to the first node and the third node of the regulation circuit;
• providing a second transistor set, electrically connecting to the second node and the third node of the regulation circuit;
• when the circuitry is operated in a first mode, turning off the regulation circuit and providing a first path from the first node to the second node by electrically connecting the third node to the first node through the first transistor set;
• and
• when the circuitry is operated in a second mode, turning off the regulation circuit and providing a second path from the second node to the first node by electrically connecting the third node to the second node through the second transistor set.

A regulation circuit, comprising:

• a first transistor, wherein a drain electrode of the first transistor connects to a first node coupling to a power source, and a source electrode of the first transistor connects to a second node coupling to a battery;
• a second transistor, wherein a gate electrode of the second transistor connects to a gate electrode of the first transistor, and a source electrode of the second transistor connects to the second node;
• and
• a third transistor, wherein a gate electrode of the third transistor connects to the gate electrode of the first transistor, and a source electrode of the third transistor connects to the first node;
• wherein the regulation circuit is configured to allow carrying a first path during a first mode and carrying a second path during a second mode.