QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 551
LITHIUM-ION BATTERY CHARGER WITH CHARGE TERMINATION
4
turns off, it remains off until a new battery is
installed, the input power is cycled, or the charger is
momentarily shut down).
Continue increasing the battery simulator power
supply until the charge current drops to
approximately 300mA (30mV on the charge current
DVM), then read the charger output voltage on the
DVM. This reading is the charger float voltage of
4.200V ± 40mV. Note: small changes in battery
simulator voltage will result in large changes in
charge current. Adjusting the simulator power
supply to 4.2V will drop the charge current to 0mA.
Sleep Mode - To verify battery drain current in the
sleep mode, remove the input supply voltage or shut
the supply off, replace the 0.1
Ω
current sense
resistor with a 1k
Ω
, and set the battery simulator
power supply to approximately 4V. The charge
current DVM will now read battery drain current with
1mV/µA.
Misc - The input voltage can range from 5.2V to 24V
with negligible effect on charge current or charge
voltage specs. When applying input voltage greater
than 20V, a solid tantalum capacitor is
recommended in parallel with the existing ceramic
input bypass capacitor to minimize voltage
transients due to ringing when the input power is hot
switched. Install a 10µF or larger, 35V tantalum
capacitor at location C2 on the demo board.
The charger can be shutdown by moving the jumper
(J1) from the “RUN” position to the “SHDN”
position.
To verify the temperature qualification feature,
remove the 10k resistor R3 and connect a resistor
substitution box to the “EXT NTC” terminals. Refer
to the LTC4002 data sheet for resistor values that
will either allow the charger to provide charge
current or stop charging because of temperature
extremes. If an actual thermistor is used, it must be
mounted near the battery, not on the board.
