Datasheet

LM3622
SNVS043B –FEBRUARY 2000–REVISED APRIL 2013 www.ti.com
FUNCTIONAL DESCRIPTION
Figure 8. LM3622 Simplified Block Diagram
The simplified LM3622 block diagram in Figure 8 gives a general idea of the circuit operation. The controller
integrates the reference, feedback and drive functions on-chip to control a linear, lithium-ion battery charger in
constant voltage and constant current (CVCC) charge operation. The regulated output voltage is sensed between
CEL and CS, and the battery charge current is sensed across a current-sense resistor between CS and GND.
The EXT pin is designed for driving a series pass element, which can be a PNP transistor or a P-MOSFET.
Tying the LV
ENB
pin to ground enables the controller's low-voltage detection circuit. When the low-voltage
detection circuit is enabled and a battery voltage below a preset threshold is detected, the LM3622 will drive the
LV pin low and shut off the current flowing into the EXT pin to suspend the CVCC charge process. The low-
voltage threshold is user selectable to be either 2.15V/cell or 2.7V/cell by pulling the LV
SEL
pin to GND or V
CC
respectively. The LV pin is a NPN open collector output that can be used to turn on a low current source to wake
up charge a deeply depleted battery. When the low-voltage detection is disabled (LV
ENB
pulled up to V
CC
), the
LM3622 always starts the charge cycle in constant current mode at any battery voltage below the controller's
regulation level, and maintains the LV pin at a high-impedance state.
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