UC1871
UC2871
UC3871
Resonant Fluorescent Lamp Driver
FEATURES
DESCRIPTION
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1µA ICC when Disabled
The UC1871 Family of IC’s is optimized for highly efficient fluorescent lamp
control. An additional PWM controller is integrated on the IC for applications re-
quiring an additional supply, as in LCD displays. When disabled the IC draws
only 1µA, providing a true disconnect feature, which is optimum for battery
powered systems. The switching frequency of all outputs are synchronized to
the resonant frequency of the external passive network, which provides Zero
Voltage Switching on the Push-Pull drivers.
PWM Control for LCD Supply
Zero Voltage Switched (ZVS) on
Push-Pull Drivers
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Open Lamp Detect Circuitry
4.5V to 20V Operation
Soft-Start and open lamp detect circuitry have been incorporated to minimize
component stress. An open lamp is detected on the completion of a soft-start
cycle.
Non-saturating Transformer
Topology
The Buck controller is optimized for smooth duty cycle control to 100%, while
the flyback control ensures a maximum duty cycle of 95%.
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Smooth 100% Duty Cycle on
Buck PWM and 0% to 95% on
Flyback PWM
Other features include a precision 1% reference, under voltage lockout, flyback
current limit, and accurate minimum and maximum frequency control.
BLOCK DIAGRAM
UDG-92061-1
Note: Pin numbers refer to DIL-18 and SOIC-18 packages only.
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