• Input Voltage Range: up to 20 V
• Voltage Options for Charging 1, 2, 3, or 4 Cells
• Output Current up to 15 mA
• Precision (0.5%) End-of-Charge Control
  • LM3420 ±1%
  • LM3420A ±0.5%
• Drive Capability for External Power Stage
• Temperature Drift Curvature Correction for Voltage Stability
• Low Quiescent Current, 85 μA (Typ.)
• Tiny SOT-23-5 package

• Lithium-Ion Battery Charging
• Suitable for Linear and Switching Regulator Charger Designs

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 amplifier's 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.