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PDF UBA2072 Data sheet ( Hoja de datos )
| Número de pieza | UBA2072 | |
| Descripción | Low Voltage Full-bridge control IC | |
| Fabricantes | NXP Semiconductors | |
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UBA2072
Low Voltage Full-bridge control IC for CCFL backlighting
Rev. 08.0 — February 2007
Preliminary data sheet
1. General description
The UBA2072 is a low voltage IC intended to drive Cold Cathode Fluorescent Lamps
(CCFLs) for back-lighting applications. The IC contains level-shifters, bootstrap diodes
and drivers for the external full-bridge power switches.
Furthermore, the UBA2072 has a build-in HF oscillator which determines the operating
frequency, a phase shift controller for obtaining constant lamp current, and a PWM
generator which is used to set the brightness level of the CCFLs.
The UBA2072 is designed to operate over a wide low voltage inverter supply range, up to
30V. The IC can be supplied directly from the inverter supply.
2. Features
Wide supply voltage range (9 V to 30 V DC)
Adjustable maximum fault timing
Integrated level-shifters
Integrated bootstrap diodes
Lamp current control
Over-voltage control
Over-current protection
Ignition failure detection
Arcing detection
Brightness level adjustment through PWM dimming
Integrated PWM generator
3. Applications
LCD-backlighting, including LCD-TV and LCD-Monitor applications. The IC is intended
to drive and control a full-bridge inverter with resonant load circuit for CCFLs, but can
also drive an array of External Electrode Fluorescent Lamps (EEFLs).
Free Datasheet http://www.Datasheet4U.com
1 page  
NXP Semiconductors
UBA2072
Low Voltage Full-bridge control IC for CCFL backlighting
7. Functional description
The UBA2072 is designed to drive a full-bridge inverter with resonant load. The load
consists typically of transformers with CCFLs. Two parameters are used by the UBA2072
to control the switches of the full-bridge inverter: the phase shift and the switching
frequency.
The two full bridge halves A and B (Figure 3) always operate at the same switching
frequency. The frequency is used to control transformer output voltage during the first
ignition of the lamps. The phase difference between the full-bridge halves A and B
voltages (VA and VB) controls the lamp current, as this determines the rms value of the
full-bridge inverter voltage VA - VB (Figure 4).
Fig 3. Full-bridge inverter definition
Fig 4. Full-bridge inverter voltage and definition of phase shift
UBA2072
Preliminary data sheet
Rev. 08.0 — February 2007
© NXP B.V. 2007. All rights reserved.
5 of 28
Free Datasheet http://www.Datasheet4U.com
5 Page 
NXP Semiconductors
UBA2072
Low Voltage Full-bridge control IC for CCFL backlighting
Fig 11. PWM dimming configurations
7.7 The fault timer
The fault timer provides a delay inbetween the detection of a fault and the shut down of
the IC (enter STOP-state). Its time Tfault(timeout) is proportional to the capacitor connected
to the CT-pin.
Any fault condition will start the timer. When the timer is activated, the capacitor at the
CT-pin will be alternatingly charged and discharged (see Figure 12). These cycles are
being counted by a four bit counter. After one cycle (the fault signalling delay Tfault(delay))
the nonFAULT-pin is activated (pulled low), to signal to any external circuit that there is a
fault detected and the IC will stop if that fault continues. After 15 cycles is the fault time-out
period Tfault(timeout) reached, and the IC will enter STOP-state.
If the fault timer is inactive, the CT-pin voltage is one Vbe (≅0.7V). The CT-timer has a
protection that prevents the IC to start-up if the CT-pin is shorted to GND.
UBA2072
Preliminary data sheet
Fig 12. Fault timer wavefporms
Rev. 08.0 — February 2007
© NXP B.V. 2007. All rights reserved.
11 of 28
Free Datasheet http://www.Datasheet4U.com
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| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet UBA2072.PDF ] | |
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