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Features
Auto-adaptive fast charge
High-resolution, accurate voltage monitoring prevents Li-Ion undercharge or overcharge
Fast charge, pre-charge and maintenance currents are provided. Different currents are selectable via external resistors.
Fast-charge termination by Δ temperature/Δ time, maximum voltage, maximum temperature, negative Δ voltage and maximum time
Dynamically detects battery insertion, removal, short circuit and bad battery without additional hardware
Supports charging of battery packs with 2–8 cells of Ni-Cd/Ni-MH or 1–4 cells of Li-Ion (1 cell of NiCd/NiMH can be supported
by added external 2x voltage amplifier)
Three optional LED indicators and Buzzer output indicate operational modes
Ni-MH/Ni-Cd charge mode, Li-Ion charge mode or discharge mode can be selected manually
Supports control of current feedback power supply and constant current power supply
Description The LM3647 is a charge controller for Lithium-Ion (Li-Ion), Nickel-Metal Hydride (Ni-MH) and Nickel-Cadmium (Ni-Cd) batteries.
The device can use either a pulsed-current charging or a constant-current charging technique. The device can also be configured
to discharge before charging. Throughout the charging sequence the LM3647 monitors voltage and/or temperature and time in
order to terminate charging.
Charge termination methods are:
Negative delta voltage (−ΔV)
Optional: Delta temperature/delta time (ΔT/Δt)
Backup: Maximum temperature
Backup: Maximum time
Backup: Maximum voltage
If both voltage and temperature fail to trigger the termination requirements, then the maximum time (configured by external
hardware) steps in which terminates the charging.
In Ni-Cd/Ni-MH mode, four different charging stages are used:
Soft-start charge
Fast charge
Topping charge
Maintenance charge
In Li-Ion mode, four different charging stages are used:
Qualification
Fast Charge Phase 1, Constant Current
Fast Charge Phase 2, Constant Voltage
Maintenance charge
The charge current of the LM3647 is configured via external resistors, which in turn controls the duty cycle of the PWM switching
control output. For cost-sensitive applications, the LM3647 charge controller cab be configured to use an external current
source and no temperature sensor.
When using an external current source, the current is controlled by the LM3647 which turns the current source on and off.
The LM3647 automatically detects the presence of a battery and starts the charging procedure when the battery is installed.
Whenever an error occurs (e.g., short circuit, temperature too high, temperature too low, bad battery, charge time over, etc.)
the LM3647 will stay in error mode until the battery is removed or it gets within the allowed charging temperature range.
The LM3647 is available in a standard 20-lead SOIC surface mount package.
Applications
Battery charging systems for:
Portable consumer electronics
Audio/video equipment
Communications equipment
Point of sale devices
Power tools
Personal convenience products
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