QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 789
SINGLE CELL LI-ION BATTERY CHARGER WITH COMPARATOR
4
ADDITIONAL COMMENTS
The charger can be put into a low quiescent current
shutdown mode by pulling the ENABLE terminal
high.
Jumpers JP2, JP3 and JP4 interact with each other
when programming charge current.
Other charge currents can be programmed by re-
moving Jumper JP3 and adding a suitable external
resistor from the CURRENT MONITOR terminal to
ground (Note that the position of JP2 and JP4 will
also determine charge current).
Likewise, other minimum charge current termina-
tion levels can be selected by selecting a suitable
resistor for R5.
The internal termination can be defeated by moving
jumper JP1 to the center position. Charge termina-
tion is then left to the user through the ENABLE
terminal.
When the minimum charge current termination
method is used and no battery is present, a
sawtooth waveform of several hundred mV p-p will
appear at the charger output. This is a function of
the output capacitor and the charger output voltage
cycling between the recharge threshold voltage and
the float voltage. The sawtooth frequency is de-
pendant on the value of the output capacitor. With a
2.2µF output capacitor, the frequency is approxi-
mately 40Hz, which will cause the CHRG LED to
appear dim. With a larger output capacitor, the LED
will flash briefly.
To speed up the 3 hour timer when evaluating the
charger circuit, replace the timing capacitor with a
much smaller value. A 300pF capacitor will reduce
the total time to approx 30 seconds.
The one Ohm resistor in series with the ceramic
input capacitor is used to minimize transient volt-
ages caused by the capacitor when the input volt-
age is quickly applied.
See LTC4062 Data Sheet for additional informa-
tion.
