UC2906
UC3906
Sealed Lead-Acid Battery Charger
FEATURES
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DESCRIPTION
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Optimum Control for Maximum The UC2906 series of battery charger controllers contains all of the necessary
Battery Capacity and Life
circuitry to optimally control the charge and hold cycle for sealed lead-acid batter-
ies. These integrated circuits monitor and control both the output voltage and cur-
Internal State Logic Provides
rent of the charger through three separate charge states; a high current
Three Charge States
bulk-charge state, a controlled over-charge, and a precision float-charge, or
Precision Reference Tracks
standby, state.
Battery Requirements Over
Optimum charging conditions are maintained over an extended temperature
Temperature
range with an internal reference that tracks the nominal temperature charac-
Controls Both Voltage and
teristics of the lead-acid cell. A typical standby supply current requirement of only
Current at Charger Output
1.6mA allows these ICs to predictably monitor ambient temperatures.
System Interface Functions
Typical Standby Supply
Current of only 1.6mA
Separate voltage loop and current limit amplifiers regulate the output voltage and
current levels in the charger by controlling the onboard driver. The driver will sup-
ply up to 25mA of base drive to an external pass device. Voltage and current
sense comparators are used to sense the battery condition and respond with
logic inputs to the charge state logic. A charge enable comparator with a trickle
bias output can be used to implement a low current turn-on mode of the charger,
preventing high current charging during abnormal conditions such as a shorted
battery cell.
Other features include a supply under-voltage sense circuit with a logic output to
indicate when input power is present. In addition the over-charge state of the
charger can be externally monitored and terminated using the over-charge indi-
cate output and over-charge terminate input.
BLOCK DIAGRAM
SLUS186 - SEPTEMBER 1996
TI [ TEXAS INSTRUMENTS ]
