FEATURES
• 1mA Typical Supply Current
• Accurate Lamp Current Control
• Analog or Low Frequency Dimming
Capability
• Open Lamp Protection
• Programmable Startup Delay
• 4.5V to 25V Operation
• PWM Frequency Synchronized to
External Resonant Tank
• 8 Pin TSSOP and SOIC Packages
Available
• Internal Voltage Clamp Protects
Transformer from Over-voltage
(UCC3973)

DESCRIPTION
Design goals for a Cold Cathode Fluorescent Lamp (CCFL) converter used
a notebook computer or portable application include small size, high efficiency,
and low cost. The UCC3972/3 CCFL controllers provide the necessary
circuit blocks to implement a highly efficient CCFL backlight power
supply in a small footprint 8 pin TSSOP package. The BiCMOS controllers
typically consume less than 1mA of operating current, improving overall
system efficiency when compared to bipolar controllers requiring 5mA to
10mA of operating current.
External parts count is minimized and system cost is reduced by integrating
such features as a feedback controlled PWM driver stage, open lamp protection,
startup delay and synchronization circuitry between the buck and
push-pull stages. The UCC3972/3 include an internal shunt regulator, allowing
the part to operate with input voltages from 4.5V up to 25V. The part
supports both analog and externally generated low frequency dimming
modes of operation.
The UCC3973 adds a programmable voltage clamp at the BUCK pin. This
feature can be used to protect the transformer from overvoltage during
startup or when an open lamp occurs. Transformer voltage is controlled by
reducing duty cycle when an over-voltage is detected.