The LM3420 series of controllers are monolithic integrated circuits designed for charging
and end-of-charge control for lithium-ion rechargeable batteries. The LM3420 is available in an
8.4-V version for one through four cell charger applications.
Included in a very small package is an (internally compensated) op amp, a bandgap
reference, an NPN output transistor, and voltage setting resistors. The amplifiers inverting input
is externally accessible for loop frequency compensation. The output is an open-emitter NPN
transistor capable of driving up to 15 mA of output current into external circuitry.
A trimmed precision bandgap reference utilizes temperature drift curvature correction for
excellent voltage stability over the operating temperature range. The LM3420 series allows for
precision end-of-charge voltage threshold for lithium-ion rechargeable batteries. The premium grade
LM3420A is available with an initial voltage threshold tolerance of ±0.5%, while the standard grade
LM3420 has an initial voltage threshold tolerance of ±1%.
The LM3420 is available in a sub-miniature 5-lead surface mount package thus allowing
very compact designs.
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