UBA2071T

General description

The UBA2071 and UBA2071A are high voltage ICs intended to drive Cold Cathode Fluorescent Lamps (CCFLs) or External Electrode Fluorescent Lamps (EEFLs) for backlighting applications. They can drive a half bridge circuit made up of two NMOSFETs with a supply voltage of up to 550 V, so the inverter can be supplied directly from a 400 V PFC bus.
The UBA2071 and UBA2071A contain a controller, a level shifter, a bootstrap diode and drivers for the external half bridge power switches. It also contains a low frequency PWM generator, which can be used to control the brightness level of the lamps, using an analog brightness/dimming control voltage. PWM dimming can also be realized, using a digital PWM input signal. PWM dimming can be synchronized with other ICs. The lamp current is controlled by means of a true zero voltage switching resonant control principle, ensuring lowest possible switch losses in the half bridge power structure.
The UBA2071 is designed to be supplied by a ∆V/∆t supply from the half bridge circuit that it drives. The IC itself needs little current and if the IC is off, a clamp protects the supply voltage from getting too high.
The UBA2071A is designed to be supplied by a fixed 12 V supply. It has a lower supply start voltage and no supply clamp.

Features

■ Suitable for operating in a very wide inverter supply voltage range (up to 550 V DC).
■ Integrated level shifter.
■ Integrated bootstrap diode.
■ Lamp current control by means of a true zero voltage switching resonant control
principle.
■ Sample & Hold circuit, maintaining current control value during PWM lamp-off
situation.
■ Separately definable time constants for current control loop and PWM dimming
attack/decay setting.
■ Overvoltage control.
■ Overcurrent protection.
■ Ignition failure detection.
■ Hard switching control.
■ Arcing detection.
■ Open/short pin protections on feedback pins.
■ Integrated, programmable fault timer.
■ Bidirectional pin acting both as fault signaling output and input, allowing external fault
interfacing to operate via the integrated fault timer.
■ Brightness level adjustment through PWM dimming.
■ Integrated PWM generator.
■ Power-down mode.
■ Communication pin for master / slave operation.
■ DC blocking capacitor pre-charging sequence.
■ Supply clamp (UBA2071 only).

Applications

■ LCD-backlighting, including LCD-TV and LCD-monitor applications. The IC is intended
to drive and control a half bridge inverter with resonant load circuit for CCFLs, but can
also drive an array of External Electrode Fluorescent Lamps (EEFLs).