LM3622 Datasheet, PDF (1/9 Pages) National Semiconductor (TI) – Lithium-Ion Battery Charger Controller

February 2000
LM3622
Lithium-Ion Battery Charger Controller
General Description
The LM3622 is a charge controller for Lithium-Ion batteries.
This monolithic integrated circuit accurately controls an ex-
ternal pass transistor for precision Lithium-Ion battery charg-
ing. The LM3622 provides a constant voltage or constant
current (CVCC) configuration that changes, as necessary, to
optimally charge lithium-ion battery cells. Voltage charging
versions (4.1V, 4.2V, 8.2V, and 8.4V) are available for one or
two cell battery packs and for coke or graphite anode battery
chemistry.
The LM3622 accepts input voltages from 4.5V to 24V. Con-
troller accuracy over temperature is ±30mV/cell for A grade
and ±50mV/cell for the standard grade. No precision exter-
nal resistors are required. Furthermore, the LM3622’s propri-
etary output voltage sensing circuit drains less than 200nA
from the battery when the input source is disconnected.
The LM3622 circuitry includes functions for regulating the
charge voltage with a temperature compensated bandgap
reference and regulating the current with an external sense
resistor. The internal bandgap insures excellent controller
performance over the operating temperature and input sup-
ply range.
The LM3622 can sink 15mA minimum at the EXT pin to drive
the base of an external PNP pass transistor. It also has
low-voltage battery threshold circuitry that removes this drive
when the cell voltage drops below a preset limit. The LV_SEL
pin programs this threshold voltage to either 2.7V/cell or
2.15V/cell. The low-voltage detection, which is a user en-
abled feature, provides an output signal that can be used to
enable a ″wake up charge″ source automatically to precon-
dition a deeply discharged pack.
The LM3622 is available in a standard 8-lead SOIC surface
mount package.
Features
n Versions for charging of 1 cell (4.1V or 4.2V) or 2 cells
(8.2V or 8.4V)
n Versions for coke or graphite anode
n Precision (±30mV/cell) end-of-charge control
n Wide input range: 4.5V-24V
n Low battery drain leakage: 200nA
n 15 mA available to drive low cost PNP
Applications
n Cellular phone cradle charger
n PDA/Notebook cradle charger
n Camcorder cradle charger
Typical Application
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