The LT3954, a DC/DC converter designed to operate as a constant-current source and constant-voltage regulator with an internal 5A switch, is now available from Linear Technology.

Usually the current for the load is produced by some kind of constant current generator (CCG), preferably with thermal stabilization of the output current. It may also be necessary to measure the ...

Grounded base PNP transistor T1 here works as a constant current generator. With 22 ohm resistor for R1, the charging current available at the output of the charger is near 50 mA.

Using pulse current charging, or a constant current divided with a few short breaks, lithium-ion batteries hold up better over hundreds of charging cycles and can last twice as long.