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UBA2072
Rev. 08.0 — February 2007
Low Voltage Full-bridge control IC for CCFL backlighting
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Preliminary data sheet
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1. General description
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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.
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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).
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NXP Semiconductors
UBA2072
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Low Voltage Full-bridge control IC for CCFL backlighting
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4. Ordering information
Table 1:
Ordering information
Package
Name
UBA2072T
UBA2072TS
SO28
SSOP28
Description
plastic small outline package; 28 leads; body
width 7.5 mm
plastic shrink small outline package; 28 leads;
body width 5.3 mm
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Type number
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Version
SOT136-1
SOT341-1
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5. Block diagram
Fig 1. Block diagram UBA2072.
UBA2072
© NXP B.V. 2007. All rights reserved.
Preliminary data sheet
Rev. 08.0 — February 2007
2 of 28
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UBA2072
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Low Voltage Full-bridge control IC for CCFL backlighting
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6. Pinning information
6.1 Pinning
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Fig 2. Pin assignment SO28 and SSOP28 package (top view)
6.2 Pin description
Table 2:
Symbol
IFB
CIFB
VFB
CVFB
IREF
CT
SGND
CF
Pin description
Pin
1
2
3
4
5
6
7
8
Description
current feedback input.
current regulation
capacitor.
voltage feedback input
voltage regulation
capacitor
reference current output
fault timing capacitor
signal ground
HF-oscillator timing
capacitor
A capacitor must be connected between this pin and the signal ground. It sets
the minimum switching frequency of the full bridge.
Function
Input signal for the lamp current control loop. Should be connected to a
voltage proportional to the lamp current.
A capacitor must be connected between this pin and the signal ground. It sets
the time constant of the lamp current control loop.
Input signal for the voltage control loop. Should be connected to a voltage
proportional to the transformer output voltage
A capacitor must be connected between this pin and the signal ground. It sets
the time constant of the voltage control loop.
A 33kΩ resistor must be connected between this pin and the signal ground.
The IC uses it to make accurate internal currents.
A capacitor must be connected between this pin and the signal ground. It sets
the time that a fault condition is allowed before the IC shuts itself down.
UBA2072
© NXP B.V. 2007. All rights reserved.
Preliminary data sheet
Rev. 08.0 — February 2007
3 of 28
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UBA2072
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Low Voltage Full-bridge control IC for CCFL backlighting
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Table 2:
Symbol
CSWP
Pin description
…continued
Pin
9
Description
phase-shift sweep
capacitor
Function
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A capacitor must be connected between this pin and the signal ground. It sets
the time in which the phase difference between bridge halve A and bridge
halve B is swept down from regulation level to zero or swept up from zero to
regulation level during PWM dimming.
If a capacitor is connected between this pin and the signal ground, it sets the
frequency of the PWM oscillator.
If this pin is connected to signal ground the internal PWM oscillator is
disabled.
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CPWM
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PWM timing capacitor
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not connected
status signal
input/output
analog PWM dimming
input
digital PWM dimming
input/output
The IC signals a fault condition to an external circuit by pulling this pin low and
external circuits can also signal a fault condition to the IC by pulling this pin
low.
The dutycycle of the internally generated PWM signal is proportional to the
voltage on this pin.
Digital output of internally generated PWM signal if a capacitor is connected to
the CPWM-pin.
Digital input of PWM signal if the CPWM-pin is connected to signal ground.
Note that the signal on the PWMd-pin is active low, so low voltage on the
PWMd-pin means lamps are on.
nonFAULT 12
PWMa
PMWd
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14
GHB
FSB
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16
high-side driver output B Gate connection of the high side power switch of full bridge halve B
floating supply output B
A buffer capacitor must be connected between this pin and the SHB-pin. This
capacitor is charged when the low side switch B is on and supplies the high
side driver B.
Return for high side gate driver B. Must be connected to the source of the high
side power switch of full bridge halve B.
A low voltage on this pin will reset and shutt down the IC
IC supply
A buffer capacitor must be connected between this pin and power ground
Gate connection of the low side power switch of full bridge halve B
return for low side drivers A and B
Gate connection of the low side power switch of full bridge halve A
Return for high side gate driver A. Must be connected to the source of the high
side power switch of full bridge halve A.
A buffer capacitor must be connected between this pin and the SHA-pin. This
capacitor is charged when the low side switch A is on and supplies the high
side driver A.
SHB
NC
EN
VDC
VDD
GLB
PGND
GLA
NC
SHA
FSA
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high-side source
connection B
not connected
chip enable input
IC low-voltage supply
input
regulated 12 V supply
output/input
low-side driver output B
power ground
low-side driver output A
not connected
high-side source
connection A
floating supply output A
GHA
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high-side driver output A Gate connection of the high side power switch of full bridge halve A
UBA2072
© NXP B.V. 2007. All rights reserved.
Preliminary data sheet
Rev. 08.0 — February 2007
4 of 28
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UBA2072
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Low Voltage Full-bridge control IC for CCFL backlighting
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7. Functional description
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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 (V
A
and V
B
) controls the lamp current, as this determines the rms value of the
full-bridge inverter voltage V
A
- V
B
(Figure
4).
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Fig 3. Full-bridge inverter definition
Fig 4. Full-bridge inverter voltage and definition of phase shift
UBA2072
© NXP B.V. 2007. All rights reserved.
Preliminary data sheet
Rev. 08.0 — February 2007
5 of 28
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