AIC1783A Datasheet, PDF (7/13 Pages) Analog Intergrations Corporation – Battery Charge Controller for Low Power Charging

AIC1783A
„ ^{APPLICATION INFORMATIONS}
OPERATION
Power-On and Battery Pre-Qualifying
When power is first applied to the AIC1783A, all
internal digital circuit blocks of the AIC1783A are
reset by the internal power-on-reset circuitry and
output LED flash 3 times to indicate the initiation of
power-on. The internal control unit then examines
the battery condition through the VBT pin.
The acceptable range of VBT pin is 0.16V to 2.7V. If
the voltage of VBT pin fails to fall within the
predetermined acceptable limits, the AIC1783A
enters a charge-suspending mode, in which all the
internal circuitry remains in reset state.
Fast Charge
After the battery passes fault checks, fast charging
begins while initial timer and safety timer of the
AIC1783A start counting. Functions of ^−ΔV
detection, peak voltage timer, and maximum battery
voltage are, however, disabled temporarily until the
initial timer period in the initial stage of a charge
cycle elapses. The initial timer period is equal to
1/80 of safety timer.
Since the low limit of acceptable VBT voltage is only
about 0.16V during the initial timer period, even
deeply discharged batteries can easily qualify to be
fast charged subsequently.
In the course of fast charge, the AIC1783A
constantly monitors the voltages at VBT pin. The
fast charge process is switched to trickle charge
when any one of the following situations is
encountered, which are explained below:
z Negative delta voltage ( ^−ΔV)
z Peak voltage timer (^0ΔV )
z Maximum charge time
z Maximum battery voltage
-ΔV Cutoff
The AIC1783A makes a voltage sampling at VBT
pin every 4 seconds when safety timer period is set
equal to 80 minutes. If a negative delta voltage of
0.25% compared to its peak value is detected at
VBT pin, the fast charge cycle is terminated.
0ΔV Cutoff
If the battery voltage stays at its peak value or
decreases very slowly for the duration determined
by the peak voltage timer which is 6% of safety
timer, the fast charge action is terminated.
Maximum Safety Timer Cutoff
The maximum fast charge period is determined by
the safety timer, which is set by a resistor
connected from TIMER pin to GND. Safety timer,
−ΔV _{, sampling rate will be longer if the resistor}
value is larger. When the value of the resistor is
100KΩ, the safety timer period equals 80 minutes.
After the safety timer period is finished, the fast
charge action is terminated.
Maximum Voltage Cutoff
The AIC1783A guards against the maximum limits
for battery voltage during fast charging. If either of
these limits is exceeded, fast charge action is
terminated.
Trickle Charge
The trickle charge after the fast charge to prevent
the loss of charge due to battery self-discharging.
The duty cycle is set to 1/128 by internal circuitry.
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