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UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
Rev. 01 -- 23 June 2008 Product data sheet
1. 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.
2. Features
I I I I I I I I I I I I I 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.
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
I Bidirectional pin acting both as fault signaling output and input, allowing external fault interfacing to operate via the integrated fault timer. I Brightness level adjustment through PWM dimming. I Integrated PWM generator. I Power-down mode. I Communication pin for master / slave operation. I DC blocking capacitor pre-charging sequence. I Supply clamp (UBA2071 only).
3. Applications
I 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).
4. Quick reference data
Table 1. Quick reference data. Tamb = 25 C; VVDD = 12 V; RIREF = 33 k; VEN = VVDD and CPWM connected to a capacitor, unless otherwise specified. All voltages are measured with respect to signal ground (SGND, pin 10). SGND and PGND connected together. Currents are positive when flowing into the IC. Symbol VSH VVDD IVDD Parameter voltage on pin SH voltage on pin VDD current on pin VDD EN pin grounded; VVDD = 14.0 V; UBA2071AT and UBA2071ATS oscillating at fsw(min); CCF = 100 pF disabled; VVDD = 11 V oscillating; CF = 100 pF; GL and GH open CCF = 100 pF; VPWMD = H; VCSWP = 0 V fsw(min) minimum switching frequency CCF = 100 pF
[1] [2] [1] [2]
Conditions
Min -
Typ -
Max 550 14 0.22
Unit V V mA
1.2 -
1.5 0.16 1.5
1.8 -
mA mA mA
1.0
1.2
1.4
mA
10 38 2.2
40 2.4
100 42 2.6
kHz kHz kHz
fsw(max)/fsw(min) maximum switching frequency to minimum switching frequency ratio Vref(creg) current regulation reference voltage
1.20
1.26
1.32
V
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
2 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
Table 1. Quick reference data. Tamb = 25 C; VVDD = 12 V; RIREF = 33 k; VEN = VVDD and CPWM connected to a capacitor, unless otherwise specified. All voltages are measured with respect to signal ground (SGND, pin 10). SGND and PGND connected together. Currents are positive when flowing into the IC. Symbol Vth(ov)(VFB) Parameter overvoltage threshold voltage on pin VFB fault time-out time driver source current driver sink resistance PWM frequency duty cycle on pin PWMD CCT = 100 nF VGL, VGH = 4 V; VVDD = VFS = 12 V VGL, VGH = 2 V; VVDD = VFS = 12 V
[1] [3]
Conditions
Min 2.40
Typ 2.50
Max 2.60
Unit V
tto(fault) Isource(drv) Rsink(drv) fPWM PWMD
0.85 -105 13.5 75 12
1.00 -90 16.0 -
1.15 -75 18.5 1000 100
s mA Hz %
[1] [2] [3]
Given frequency is switching frequency of GL and GH. Sawtooth frequency on CF pin is twice as high. Can be set by external capacitor PWMD is active low: A low level on the PWMD pin corresponds with lamps-on. Example: PWM = 20 % means PWMD is during 20 % of each cycle low and the lamps are 20 % of the time on, resulting in a light output of 20 %.
5. Ordering information
Table 2. Ordering information Package Name UBA2071T UBA2071AT UBA2071TS UBA2071ATS SO24 SO24 SSOP24 SSOP24 Description plastic small outline package; 24 leads; body width 7.5 mm plastic small outline package; 24 leads; body width 7.5 mm plastic shrink small outline package; 24 leads; body width 5.3 mm plastic shrink small outline package; 24 leads; body width 5.3 mm Version SOT137-1 SOT137-1 SOT340-1 SOT340-1 Type number
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
3 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
6. Block diagram
NONFAULT CT
bootstrap diode
IREF VDD SGND EN
INTERNAL SUPPLY AND REFERENCE CIRCUITS CONTROL
VDD TIMER LEVELSHIFTER
FS
GH
high-side driver
NON-OVERLAP TIMING CF HF OSCILLATOR HARDSWITCHING DETECTION
SH VDD
GL
low-side driver
CSWP CVFB
TRACK AND SWEEP
PGND
MASTER / SLAVE COMMUNICATION VFB OVERVOLTAGE SENSING ARCING DETECTION OVERCURRENT DETECTION PWM GENERATOR IFB DOUBLE SIDE RECTIFIER LAMP CURRENT SENSING
COMM
UBA2071
CIFB PWMA PWMD CPWM
014aaa098
Fig 1.
Block diagram
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
4 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
7. Pinning information
7.1 Pinning
IFB CIFB VFB CVFB CSWP CT CF IREF CPWM
1 2 3 4 5 6 7 8 9
24 GH 23 FS 22 SH 21 n.c. 20 n.c. 19 n.c. 18 GL 17 PGND 16 VDD 15 EN 14 PWMA 13 PWMD
014aaa099
UBA2071
SGND 10 COMM 11 NONFAULT 12
Fig 2.
Pin assignment SO24 and SSOP24 package (top view)
7.2 Pin description
Table 3. Symbol IFB CIFB VFB CVFB CSWP Pin description Pin 1 2 3 4 5 Description current feedback input. current regulation capacitor. voltage feedback input voltage regulation capacitor frequency sweep capacitor fault timing capacitor HF-oscillator timing capacitor reference current output PWM timing capacitor 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 capacitor must be connected between this pin and the signal ground. It sets the time in which the HF frequency is swept up from regulation level to the maximum frequency and back during PWM dimming. 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 down itself. A capacitor must be connected between this pin and the signal ground. It sets the minimum switching frequency of the half bridge. A 33 k resistor must be connected between this pin and the signal ground. The IC uses it to make accurate internal currents. 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. SGND COMM 10 11 signal ground master / slave communication Via this pin the IC can communicate with a dedicated slave device.
CT CF IREF CPWM
6 7 8 9
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
5 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
Table 3. Symbol
Pin description ...continued Pin Description status signal input/output digital PWM dimming input/output Function The IC signals a fault condition to external circuits by pulling this pin low. Also external circuits can signal a fault condition to the IC by pulling this pin low. 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. Remark: The signal on the PWMD pin is active low, so low voltage on the PWMD pin means lamps are on.
NONFAULT 12 PWMD 13
PWMA EN
14 15
analog PWM dimming input chip enable input
The duty cycle of the internally generated PWM signal is proportional to the voltage on this pin. A low voltage on this pin will reset and shut down the IC. This pin is also used to select between DC blocking capacitor charging mode and normal operation. A buffer capacitor must be connected between this pin and power ground. return for the low-side driver. Gate connection of the low-side power switch. HV spacer pin. HV spacer pin. HV spacer pin. Return for high side gate driver. Must be connected to the source of the high-side half bridge power switch. A buffer capacitor must be connected between this pin and the SH pin. This capacitor is charged when the low-side power switch is on and supplies the high-side driver when the high-side power switch is on. Gate connection of the high-side half bridge power switch.
VDD PGND GL n.c. n.c. n.c. SH FS
16 17 18 19 20 21 22 23
supply input power ground low-side driver output not connected not connected not connected high-side source connection floating supply
GH
24
high-side driver output
8. Functional description
The UBA2071 and UBA2071A are designed to drive a half bridge inverter (as shown in Figure 3) with a resonant load. The load consists typically of a transformer with CCFLs or EEFLs. The IC has an AC lamp current sense input (IFB). It regulates the average absolute value of the lamp current by varying its switching frequency. The load is presumed to be inductive: higher frequency results in lower lamp current. The UBA2071 and UBA2071A include a PWM dimming function. The ICs switch the lamps on and off with a frequency lower than the lamp current frequency but higher than what the human eye can see. The light output of the lamps can be set by setting the ratio of the on-time and off-time. These ICs have several forms of protection and the next chapters will describe each function in more detail.
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
6 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
VHV
UBA2071
FS GH VDD SH
CFS QHS
VHB
QLS
LOAD
0.5 VHV
Cblock
GL PGND
014aaa100
Fig 3.
Basic half bridge inverter
8.1 Supply, Start-up and UnderVoltage LockOut (UVLO)
start up current
UBA2071
VDD
C1
AUXILARY SUPPLY
014aaa101
Fig 4.
Supply configuration (for UBA2071 only)
The UBA2071 is supplied via the VDD pin as shown in Figure 4. The supply voltage is either made by the inverter itself, using a V/t or is a auxiliary fixed supply voltage. A start-up current source that can supply minimal Istartup(VDD) is needed for start-up. This can be a resistor to the half bridge supply voltage. The IC starts up when the voltage at the VDD pin goes over Vstartup(VDD) and shuts down when the voltage at the VDD pin drops below Vstop(VDD) and the output GL is high1. The hysteresis between the start and stop levels allows the IC to be supplied by the supply buffer capacitor (C1 in Figure 4) until the auxiliary supply is settled. The auxiliary supply must not exceed the maximum voltage allowed on the VDD pin and has to be above Vstop(VDD). The UBA2071A can directly be supplied by a fixed voltage source on the VDD pin. The voltage supplied by this source has to be above the maximum value of Vstartup(VDD) but below the maximum of VVDD. Typically it will be a 12 V 5 % source.
1.
When both GH and GL are low, during the lamps-off period of PWM dimming (PWMD is high), the IC will shut down until the PWMD is low and the GL is high again.
(c) NXP B.V. 2008. All rights reserved.
UBA2071_A_1
Product data sheet
Rev. 01 -- 23 June 2008
7 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
8.2 VDD clamp
When the UBA2071 is disabled (EN pin low) or in the stop state, the VDD clamp is activated. The VDD clamp is an internal active zener limiting the voltage to Vclamp(VDD). It prevents the start-up current source from charging the VDD buffer capacitor to too high a voltage. The maximum current that is allowed to be delivered by the start-up current source is determined by the clamp voltage as stated in Table 6 and the maximum allowed VDD voltage as stated in Table 4. The UBA2071A has no VDD clamp.
8.3 Enable
The UBA2071 or UBA2071A can be activated or set to standby via the EN pin. If the voltage on the EN pin is below Vth(L)(EN), the IC will stop oscillating at the next GL high state2, and most parts of the internal circuits will shut down. When the EN pin is left open, it is pulled low by an internal bias current of Ibias(EN). When the voltage on the EN pin comes above Vth(H)1(EN), the IC will start up in DC blocking capacitor charging mode (see Section 8.8). When the voltage on the EN pin goes over Vth(H)2(EN), the IC will start with the initial ignition frequency sweep (see Section 8.8) and subsequently go to normal operation mode again.
8.4 The oscillator
The UBA2071 and UBA2071A have an internal voltage controlled sawtooth oscillator, see Figure 5. Its frequency inverses in proportion to the capacitor connected to the CF pin. The IC switches GL on and GH off during one oscillator period and GL off and GH on during the next oscillator period. This results in a half bridge voltage with a frequency (called the switching frequency fsw from here on) of half the oscillator frequency and with a duty cycle of exactly 50 %. The oscillator frequency is controlled by changing the charge current at the CF pin. By changing the frequency the lamp current is controlled. It is also used to limit the transformer output voltage and for gradually switching the lamps on and off during PWM dimming.
2.
When both GH and GL are low during the lamps off period of PWM dimming (so PWMD is high), the IC will wait with entering the standby state until PWMD becomes low again and GL can be made high.
(c) NXP B.V. 2008. All rights reserved.
UBA2071_A_1
Product data sheet
Rev. 01 -- 23 June 2008
8 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
VCFH VCF 0 VDD VGH - VSH 0 VDD VGL 0 VHV VHB 0 tno
014aaa102
t
t
t
t
Fig 5.
Oscillator, driver and half bridge voltages
8.5 Non-overlap
During each transition between the two states GL high/GH low and GL low/GH high, GL and GH will both be low for a fixed time tno (non-overlap time) to allow the half bridge point to be charged or discharged by the load current (presuming the load always has an inductive behavior), and thus enabling zero voltage switching, see Figure 5.
8.6 Low-side and high-side drivers
The low-side and high-side drivers are identical. The output of each driver is connected to the equivalent gate of an external power MOSFET. The high-side driver is supplied by the bootstrap capacitor, which is charged from the VDD voltage via an internal diode when the low-side power MOSFETs is on. The low-side driver is directly supplied by the VDD voltage.
8.7 DC blocking capacitor charging
When the IC is off, either because VVDD is too low, it is disabled via the EN pin, or it stopped after the time-out period during a fault condition, the low-side power switch (QLS in Figure 3) is turned on by making GL high. This ensures that the supply buffer capacitor of the floating supply (CFS in Figure 3) is fully charged at start-up. As a side effect the DC blocking capacitor (Cblock in Figure 3) will be completely discharged at start-up. To prevent large inrush currents during the first switching cycles the UBA2071 and UBA2071A can first charge the DC blocking capacitor at start-up.
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
9 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
When the voltage on the EN pin goes over Vth(H)1(EN) after the IC has been disabled (EN pin below Vth(L)(EN)) the IC will start up in DC blocking capacitor charging mode3. When the voltage on the EN pin goes over Vth(H)1(EN) after the IC has been off (EN pin below Vth(L)(EN) or VDD below Vstop(VDD)) the IC will start up in DC blocking capacitor charging mode. When the voltage on the EN pin goes over Vth(H)2(EN) the IC will continue with the initial ignition frequency sweep and normal operation mode. Figure 6, EN configuration, shows three examples of how the enable input can be used:
UBA2071
EN
C1
R1
enable
(1)
VHv
R2
VHv
R2
UBA2071
EN
R3
R4
VCblock
UBA2071
Cblock
EN
R3
R4
VCblock
Cblock
R5
disable
(2)
(3)
014aaa253
Fig 6.
EN configuration
1. Digital enable input with DC blocking capacitor charging. R1 and C1 define a fixed DC blocking capacitor charging time. Remark: The digital input signal high level has to be above the maximum value of Vth(H)2(EN). 2. Sensing of HV supply and DC blocking capacitor voltages via the EN pin. The IC will start in DC blocking capacitor charging mode if VVDD is above Vstartup(VDD) and VHV is above ( ( R2/R4 ) + ( R2/R3 ) + 1 ) x V th(H)1(EN) . It will then go into initial ignition frequency sweep and normal operation mode once VCblock has been charged to ( ( ( R4/R2 ) + ( R4/R3 ) + 1 ) x V th(H)2(EN) - R4/R2 x V HV ) . 3. Sensing of HV supply and DC blocking capacitor voltages via the EN pin combined with digital enable input. In DC blocking capacitor charging mode the low-side power switch (QLS in Figure 3) is turned on for a period ((1/fsw(max)) - tno) and then the high-side power switch (QHS in Figure 3) is turned on for a period ((1/fsw(max)) - tno) followed by a period of (3/fsw(min)) during which both power switches are off. This is repeated until the mode is left. When leaving the DC blocking capacitor charging mode by raising the EN pin above Vth(H)2(EN), the running cycle of the DC blocking capacitor charging mode will first be completed (see Figure 7).
3.
When the enable input is kept high during the time that the IC is off, because the supply voltage is too low, the IC might not start in DC blocking capacitor charging mode.
(c) NXP B.V. 2008. All rights reserved.
UBA2071_A_1
Product data sheet
Rev. 01 -- 23 June 2008
10 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
(H)2(EN) EN (H)1(EN) (L)(EN) 0 GH VSH
GL
0 0.5 T disabled DC blocking capacitor charging
014aaa252
7.5 T 3 / fsw(min)
T 1 / fsw(max)
7.5 T 3 / fsw(min) initial ignition sweep and normal mode
Fig 7.
DC blocking capacitor charging mode
Remark: Due to the nature of the charging sequence, VCblock will automatically be charged to 0.5 x VHV (when given enough time). If the IC is kept in DC blocking capacitor charging mode longer than necessary, VCblock will remain 0.5 x VHV. Therefor the time constant made by R1 and C1 in example A in Figure 6, is not critical. However, since VCblock cannot become more than 0.5 x VHV, it is important to take a lower target value for VCblock than 0.5 x VHV (with enough margin) in examples B and C of Figure 6, otherwise the IC may get stuck in DC blocking capacitor charging mode.
8.8 Lamp (re-)ignition
The IC starts at its maximum switching frequency fsw(max). The lamp current and the lamp voltage control loops are enabled. The frequency is swept down towards the minimum frequency fsw(min), see Figure 9. During this initial ignition frequency sweep the lamp voltage will increase as the frequency comes closer to the resonant frequency of the unloaded resonance circuit. Once the ignition voltage Vign is reached the lamps will ignite and the lamp voltage will drop4 to the voltage of the loaded resonance curve, see Figure 8.
4.
For CCFLs only.
(c) NXP B.V. 2008. All rights reserved.
UBA2071_A_1
Product data sheet
Rev. 01 -- 23 June 2008
11 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
Vlamp (V)
(1)
Vign
(2)
Vburn
fsw(min) freg fign f (kHz)
fsw(max)
014aaa103
(1) Indicates lamp-OFF. (2) Indicates lamp-ON.
Fig 8.
Initial ignition of cold cathode fluorescent lamp via frequency sweep and load resonance
Advantage of the sweep rather than a fixed ignition frequency is that sensitivity for spread in resonance frequency is much lower. Once the lamps are ignited the frequency sweep-down continues, gradually increasing the lamp current (the resonance circuit should now still be inductive, so current increases as frequency drops) until the current regulation level is reached (at fsw = freg). The frequency will not reach fsw(min) if the lamp current comes into regulation. Once it has been detected that the lamps are on (if the average absolute voltage at the current feedback input (pin IFB) is above Vth(lod)(IFB)) PWM dimming is enabled. See Figure 9. The initial ignition frequency sweep and the PWM generator are not synchronized. Once the regulation frequency is reached, PWM dimming can start anywhere in its cycle. A small internal PWM dimming enable delay time, td(en)PWM, allows the lamps to settle before PWM dimming starts. At the start of the lamps-off period of the PWM dimming, the switching frequency is swept up to fsw(max). This reduces the lamp voltage so the lamps go out. If fsw(max) is reached, both GL and GH are made low, so both half bridge powers will be non-conducting. This is indicated by the dotted part of the switching frequency (fsw) line in Figure 9.
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
12 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
ignition max fsw
fign freg min 0 ov t
Vsec
0 VCVFB
t
max VCVFB VCIFB VCSWP 0
VCIFB
VCSWP
t
VPWMD
0
t
nom Ilamp
0
initial ignition sweep
PWM-enable delay steady-state
t
014aaa104
Fig 9.
Initial ignition frequency sweep and PWM dimming frequency sweep signals
The lamps start switching again on period GL and GH and the frequency is swept back to the regulation frequency freg. The duration of the PWM frequency sweep is inverse proportional to the capacitor connected to the CSWP pin.
8.9 Overvoltage control
The overvoltage control circuit is intended to prevent the transformer output voltage from exceeding its maximum rating. It can also be used to regulate the output voltage to the required lamp ignition voltage. Under normal circumstances the capacitor at the CVFB pin is charged by a constant bias current Ich(CVFB), thus the voltage on the CVFB pin will increase resulting in a decrease of switching frequency. If the IC is in current regulation this bias current will flow away via a tracking circuit which makes the voltage on the CVFB pin following the voltage on the CIFB pin, see Figure 11.
UBA2071_A_1 (c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
13 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
When the voltage on the VFB pin exceeds Vth(ov)(VFB), a fault condition is signalled (for handling of fault conditions, see Section 8.14) and the bias current at the CVFB pin changed to the discharge current Idch(CVFB). As a result, the switching frequency increases and the output voltage of the transformer will decrease5. As soon as the voltage at the VFB pin drops below Vth(ov)(VFB), the CVFB capacitor is charged again and the output voltage of the transformer will increase again. Because the charging and discharging of the CVFB capacitor follows the ripple on the VFB pin voltage, the feedback gain of the voltage control loop is set by the ripple on the feedback signal. The voltage at the CVFB pin is limited by the oscillator circuit to VCVFB(max) when the minimum switching frequency fsw(min) is reached, see Figure 10. This ensures an immediate frequency increase when overvoltage is detected.
fsw(max)
frequency
fsw(min)
0
VCVFB(max) Voltage on CVFB-pin
014aaa105
Fig 10. Frequency function of CVFB voltage
8.10 Lamp current control
The lamp current control is always active when the IC is on, except if the lamps are off during PWM dimming. The AC lamp current is sensed by an external resistor connected to the IFB pin, see Figure 11. The resulting AC voltage on the IFB pin is internally Double-Sided Rectified (DSR) and compared to a reference level Vref(creg) by an Operational Transconductance Amplifier (OTA). When the current is being regulated, switch S1 is closed (conducting). The output current of the OTA is fed into capacitor C1, which is connected to the CIFB pin. So C1 is charged and discharged according to the voltage on the IFB pin.
5.
Presuming that the load impedance is in inductive region.
(c) NXP B.V. 2008. All rights reserved.
UBA2071_A_1
Product data sheet
Rev. 01 -- 23 June 2008
14 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
Ich(CSWP)
Idch(CSWP)
to CCFLs
OTA
IFB
DSR R1 Vref(creg) S1
0 PWMD
1
S2
to VCO
Ich(CVFB)
UBA2071
CIFB
C1
CVFB
C2
CSWP
C3
014aaa106
Fig 11. Lamp frequency control circuit
Under normal operating conditions, the voltage across capacitor C2, which is connected to the CVFB pin, will follow the voltage on the CIFB pin. During the lamps-on period of the PWM dimming, the voltage across C3, which is connected to the CSWP pin, will follow the voltage on the CVFB pin and therefore also the voltage on the CIFB pin. The voltage on the CSWP pin is connected to the VCO input of the HF oscillator and thus controls the switching frequency. If the load is assumed to be inductive an increase in the frequency will cause a decrease in the lamp current, while a decrease in the frequency will cause an increase in the lamp current. The advantage of having a separate current regulation loop timing capacitor pin CIFB next to the voltage regulation loop timing capacitor CVFB is that time constants for both loops can be set independently. The separate PWM dimming sweep timing capacitor pin CSWP makes it possible to set the PWM dimming sweep speed independent of the current and voltage regulation loops.
8.11 PWM dimming
Pulse Width Modulation (PWM) dimming is a method of reducing the average lamp light output by switching the lamps on and off with a repetition rate or PWM frequency, fPWM, high enough not to be seen by the human eye (but much lower than the inverter frequency fsw). By varying the lamp-on to lamp-off, period ratio, called the duty cycle PWM, the light output can be varied over a wide range. The voltage at the CSWP pin determines the actual switching frequency, it inverses in proportion to the switching frequency. During the lamps-on period of the PWM dimming it follows the voltage at the CVFB pin (the current Ich(CSWP) is drained by the tracking circuit between the CVFB pin and the CSWP pin). Just prior to transitioning towards the lamps-off period of the PWM dimming the lamp current control loop, see Figure 11, is opened by opening switches S1. The voltage on the CSWP pin is swept down, decaying the lamp current, leading in the PWM lamp-off situation, after which the half bridge switch actions are stopped, resulting in true zero lamp current. see Figure 9. In the meantime the regulation level is preserved in C1 and C2. The
UBA2071_A_1 (c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
15 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
PWM lamp-on situation is reached again through a reverse sequence of events, starting the half bridge actions, increasing the voltage on CSWP, increasing the lamp current back to the controlled value. Switch S1 is closed (conducting) again when the voltage on the CSWP pin has reached the voltage on the CVFB pin again. The IC waits until the CSWP sweep-up6 has reached the current/voltage control level at the CVFB pin before sweeping down. This prevents the lamps from going out completely when deep dimming on CSWP pin is combined with a large value capacitor. After the switching frequency has reached fsw(max), both GL and GH are made low, so both half bridge powers will be non-conducting, see Figure 12. This guarantees zero lamp current during the PWM-off period7, while the CSWP frequency sweep acts as soft stop and soft restart, of which the softness can be set by the value of the capacitor connected to the CSWP pin.
max reg VCSWP
0
t
5V VPWMD 0 t
VDD VGH - VSH
0
t
VDD VGL
0
t
014aaa107
Fig 12. PWM dim cycle waveforms
Three pins are available to configure the internal PWM generator: the CPWM pin, PWMA pin, and the PWMD pin. The two possible PWM configurations are shown in Figure 13. In the analog or master mode the internal PWM generator is active and generating the PWM signal. This signal is put on the PWMD pin, which is automatically configured as an output. The minimum duty cycle of the internal PWM generator is limited to PWM(min).
6. 7.
CSWP sweep-up is frequency sweep-down. Until the ringing of voltage on the half bridge point has died away, some (capacitive) current may still cause a light glow at the hot side of the lamps. Therefore it is advised to maximize the attenuation of the ringing circuit (made up by the transformer inductance and the V/t limiting capacitor).
(c) NXP B.V. 2008. All rights reserved.
UBA2071_A_1
Product data sheet
Rev. 01 -- 23 June 2008
16 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
CPWM
C1
9
CPWM
9
analog in
PWMA 14
RPWMA
PWMA 14
VPWMA(ref)
PWM out
PWMD 13
PWM in PWMD 13 PWM intern
PWM intern
UBA2071
A: analog or master mode
UBA2071
B: digital or slave mode
014aaa108
Fig 13. PWM dimming configurations
When the CPWM pin is connected to ground the IC is put in digital or slave mode and the PWMD pin is an input. The internal PWM generator is not used. The IC uses the PWM signal provided on the PWMD pin. PWM dimming of multiple ICs can be synchronized by configuring one IC as master and the others as slaves and connecting all PWMD pins together. The PWMD input/output is active low. A voltage below Vth(L)(PWMD) on the pin will turn the lamps on, while a voltage above Vth(H)(PWMD) will turn the lamps off. PWM dimming is only enabled in normal mode, when no fault condition exists. The only exception is when an external detected fault condition is entered via the NONFAULT pin, then PWM dimming remains active, see Figure 15.
8.12 The fault timer
The fault timer provides a delay in between the detection of a fault and the shutdown of the IC (enter STOP state). Its time is controlled by a capacitor at the CT pin. Any fault condition will start the timer. When the timer is activated, the capacitor at the CT pin will be alternatively charged and discharged, see Figure 14. After the fault output delay time, td(o)fault), the NONFAULT pin is activated (pulled low). This is to signal to any external circuit that a fault has been detected and the IC will stop if that fault continues. After the fault time-out period tto(fault) is reached the IC will enter STOP state.
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
17 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
VCT
0
t
VNONFAULT
0 td(o)fault tto(fault)
t IC in STOP-state
014aaa110
Fig 14. Fault timer waveforms
If the fault timer is inactive, the CT pin voltage is 1 Vbe, about 0.7 V. The CT timer has a protection that prevents the IC to start up if the CT pin is shorted to GND.
8.13 Communication
The UBA2071 and UBA2071A have a dedicated communication pin, the COMM pin, for communicating with a slave half bridge driver (like the UBA2073), for instance for use in a balanced half bridge driver configuration. Via the COMM pin, a clock signal and a signal to indicate that both half bridge powers are to be turned off are exported and a fault signal is imported. The clock signal is a digital signal with a low level VL(clk)(COMM) and a high level VH(clk)(COMM). To signal that both half bridge powers should be turned off, the voltage at the COMM pin is raised to VO(hbswoff)(COMM). The UBA2071 and UBA2071A look at the current drawn from the COMM pin during the clock high period for a hard switching signal from the slave half bridge driver. First, a non-overlap time period tno is discarded to prevent that a capacitive load on the communication line is seen as a signal. Then the detected current is averaged over the clock high period before being compared to the reference level Ith(det)hsw(COMM). The current value is sampled on the falling edge of the clock signal and held during the clock low period. The received signal is treated as equal to an internal hard switching detection (so PWM dimming will be disabled, switching frequency will be increased and fault timer will be started). When only the UBA2071 or UBA2071A is used, the COMM pin must be "not connected".
8.14 Protections
All fault conditions and how they are processed in the IC can be found in Figure 15. The UBA2071 and UBA2071A have the following protections:
* OverVoltage Protection (OVP), * OverVoltage Extra protection (OVE),
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Product data sheet
Rev. 01 -- 23 June 2008
18 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
* * * * * *
OverCurrent Protection (OCP), bad contact or ARCing (ARC), Ignition Failure (IF), open or shorted current feedback (IFB pin open/short), open or shorted voltage feedback (VFB pin open/short) Hard Switching (HS).
There are also two pins, the NONFAULT pin and the COMM pin, via which a fault can be signalled to the IC, by an external circuit.
enable low_supply NONFAULT-pin_fault_signal IFB_open / short over_voltage_extra over_voltage VFB_open / short over_current f_max arcing_detected COMM-pin_fault_signal hard_switching_detected FILTER FAULTTIMER stop
ic_off lamp_current_detected f_min
R Q S
lamp_on ignition_ failure R Q S DELAY enable_PWM_ dimming
014aaa111
Fig 15. Simplified control schematic
The fault protection functions are explained in the following sections.
8.14.1 Voltage feedback open or short protection
If the VFB pin is left open or shorted to SGND, the voltage at the VFB pin will drop below the VFB open/short protection threshold voltage Vth(osp)VFB, due to the internal bias resistor Ri(VFB). If the voltage at the VFB pin is below Vth(osp)VFB continuously or only during a part of each switching cycle the PWM dimming is disabled and the fault timer is started. To protect the inverter transformer(s) against overvoltage if the voltage feedback loop is broken, the frequency stays at fsw(max) or is increased by discharging the capacitor at the CVFB pin (by Idch(CVFB)). For this function the voltage at the VFB pin has to be below Vth(osp)VFB during more than 50 % of each switching cycle.
UBA2071_A_1
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Product data sheet
Rev. 01 -- 23 June 2008
19 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
8.14.2 Overvoltage protection
The overvoltage control, see Section 8.9, is intended to prevent the transformer output voltage from exceeding its maximum rating. The overvoltage control level has to be at least at the required lamp ignition voltage, otherwise the lamps may not ignite. Once the lamps are on and in steady state, the transformer output voltage will usually be about half the required ignition voltage for CCFLs. Thermal design of the transformers is based on this lower voltage, not on the ignition voltage above which the overvoltage control has to be. Hence the circuit might not stay in overvoltage regulation indefinitely. Therefore overvoltage regulation is combined with overvoltage protection. When the voltage on the VFB pin exceeds the OV reference level Vth(ov)(VFB), the CVFB is discharged, an overvoltage fault condition is signalled, PWM dimming is disabled, and the fault timer is started. An internal latch makes the OV fault signal continuously high, even if the voltage at the VFB pin only exceeds Vth(ov)(VFB) during part of the output period. So the peak of the voltage on the VFB pin determines if an overvoltage fault condition is seen. An internal filter prevents the overvoltage fault condition from being reset when the voltage at the VFB pin drops below the OV reference level for only one or two hf cycles. In order to avoid an OV fault condition at the nominal switching frequency (with the lamps operating normally), the voltage ripple on the VFB pin must not be too large.
8.14.3 Hard switching protection
As the UBA2071 and UBA2071A are intended to drive a half bridge at a high voltage, a feature is included to ensure zero voltage switching. The design of the resonant load should guarantee zero voltage switching under normal operating conditions. To prevent overheating due to high switching losses in case of any abnormal operating condition, hard switching of the half bridge is detected internally. At the moment the high-side switch is turned on, the voltage step at the SH pin is measured. If it is above Vth(hsw)(SH) then PWM dimming is disabled and the fault timer is started. Also, the frequency is increased by discharging the capacitor at the CVFB pin (by Idch(CVFB)).
8.14.4 Overvoltage extra protection
Though the hard switching protection as described in Section 8.14.3, usually prevents the circuit from getting at the wrong side of the resonance curve of the load (were the load shows capacitive behavior), this might happen for instance when a lamp is suddenly disconnected. The parasitic capacitance of the lamp and its connection wire may make up a significant part of the resonance circuit capacitance, so if a lamp is disconnected the resonance frequency of the remaining load is suddenly higher and the switching frequency might be at the capacitive side. Hard switching will occur and be detected. The result is an increase in the switching frequency, which will make the situation worse: the switching frequency comes closer to the resonance frequency of the remaining load, creating a higher and potentially destructive transformer secondary voltage. The OverVoltage Extra (OVE), protection prevents damage to the circuit by adding an extra overvoltage protection level with quick response to that. When the voltage on the VFB pin exceeds this OVE level Vth(ovextra)(VFB), an OVE fault condition is signalled. The IC will stop if this happens during a couple of subsequent hf cycles. The time it takes before the IC stops depends on a percentage of the time the VFB pin voltage exceeds the OVE level and if hard switching is detected also. Figure 16 shows typical shutdown response
UBA2071_A_1 (c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
20 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
times in case overvoltage and overvoltage extra are detected at the same moment (curve (1)) and if overvoltage, overvoltage extra and hard switching are detected at the same moment (curve (2)). The first parts of the curves are dashed because an internal filter makes that VFB needs to be above Vth(ovextra)(VFB) for at least about 1 s for the overvoltage extra to react at all. If a normal overvoltage fault was already present for more than about 840 s before overvoltage extra detection started or hard switching was already detected for more than about 55 s before overvoltage extra detection started, then the IC will shut down about 1 s after overvoltage extra is detected.
500 stop time (s) 400
014aaa112
300
200
(1)
100
(2)
0 0 20 40 60 80 100 VFB above OVE (%)
Fig 16. Shutdown time at over voltage extra detection
8.14.5 Current feedback open or short protection
If the IFB pin is left open or shorted to SGND, the peak of the absolute value of the voltage at the IFB pin will be below the IFB open/short protection threshold Vth(osp)(IFB) and the fault timer is started. The IFB open/short protection looks only at the IFB pin voltage if the voltage at the CSWP pin is equal to the voltage at the CVFB pin. During PWM dimming this is when the lamps are on and in current regulation or voltage regulation (so not during PWM lamps-off period and not during the re-ignition frequency sweep).
8.14.6 Overcurrent detection
When the peak of the absolute value of the voltage across the current sense resistor (connected to the IFB pin) exceeds the OC reference level Vth(ocd)(IFB) and the IC is oscillating at fsw(max), overcurrent is detected. As result PWM dimming is disabled and the fault timer is started.
8.14.7 Arcing detection
If arcing occurs, for instance due to a bad lamp connection, it causes repetitive short current spikes that can be seen as voltage spikes at the IFB input. The arcing detection circuit is directly connected to the IFB pin, so it can only see spikes with a positive polarity. Usually that will be sufficient. It can detect spikes with amplitude above Vth(det)arc(IFB) and a
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Product data sheet
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NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
duration longer than tspike(min). Each spike will trigger an internal one-shot, which signals to the control circuits that arcing has been detected. When arcing is detected, PWM dimming is disabled and the fault timer is started.
8.14.8 Ignition Failure (IF)
When the current control loop comes close to its regulation point, the lamps are assumed to be on (ignited). This is when the average absolute voltage on the IFB pin is above Vth(lod)(IFB). If the lamps are not on when the ignition sweep is finished, (switching frequency has reached fsw(min)), then an ignition failure is detected, PWM dimming is disabled and the fault timer is started.
8.14.9 The NONFAULT pin
The NONFAULT pin provides bidirectional signalling of the fault status between the IC and any external circuit. When no fault is detected, the voltage on the pin is pulled high to Voc(NONFAULT) by an internal current source. An external circuit can signal to the IC that a fault has been detected by pulling a current larger than Itrig(I)NONFAULT from the NONFAULT pin. The IC will detect the current drawn from the pin and start the fault timer. To prevent interference with the PWM dimming, the IC will only look at the NONFAULT pin during the period when the lamp current regulation loop is closed (when V CSWP = V CVFB ). When the IC detects an internal fault, see Section 8.14.2 to Section 8.14.8), it signals this via the NONFAULT pin by pulling the pin down (after the fault output delay time td(o)fault)). At this point the IC can no longer detect the external fault. However, by then the fault timer is already running.
NONFAULT pin voltage Voc(NONFAULT) Vtrig(I)NONFAULT load line
1V
in: low (active) out: high (inactive)
0 in: high (inactive) out: high (inactive)
in: unknown out: low (active)
NONFAULT pin current
Isc(NONFAULT)
Itrig(I)NONFAULT
Isink(NONFAULT)
014aaa113
Fig 17. Input and output levels at the NONFAULT pin
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
22 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
The signal from the IC is a voltage signal and the signal to the IC is a current signal. In this way a driving conflict is prevented. Also, it leaves the possibility for the outside world to see the signal from the IC even while a fault condition is being signalled to the IC in the meantime, as illustrated in Figure 18.
UBA2071
to IC from IC NONFAULT
014aaa114
Fig 18. Splitting the NONFAULT pin signals to and from the IC
8.14.10 Fault input via the COMM pin
If a fault is signalled to the IC via the COMM pin this fault is treated identical to hard switching detected, see Section 8.14.3.
9. Limiting values
Table 4. Limiting values In accordance with the Absolute Maximum Rating System (IEC 60134). All voltages are measured with respect to signal ground (SGND pin 10). Symbol General Rref(IREF) SR Tamb Tj Tstg Voltages VSH VVDD VFS voltage on pin SH voltage on pin VDD voltage on pin FS continuous t < 0.5 s with respect to VSH VGL VGH VPGND VVDD VCOMM VEN VPWMA VPWMD
UBA2071_A_1
Parameter reference resistance on pin IREF slew rate ambient temperature junction temperature storage temperature
Conditions
Min 30
Max 36 +4 +100 +125 +150 550 14 +570 +630 +14 +14 +14 0.0 +14 +14 +14 +5 +5
Unit k V/ns C C C V V V V V V V V V V V V V
on pins FS, GH, and SH
-4 -25 -25 -55 0 0 -0.3 -0.3 -0.3 0.0 -0.3 -0.3 -0.3 -0.1 -0.1
voltage on pin GL voltage on pin GH voltage on pin PGND voltage on pin VDD voltage on pin COMM voltage on pin EN voltage on pin PWMA voltage on pin PWMD with respect to VSH
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Product data sheet
Rev. 01 -- 23 June 2008
23 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
Table 4. Limiting values ...continued In accordance with the Absolute Maximum Rating System (IEC 60134). All voltages are measured with respect to signal ground (SGND pin 10). Symbol VNONFAULT VVFB VIFB ESD VESD electrostatic discharge voltage human body model: pins IFB, CIFB, VFB, CVFB, CSWP, IREF, CT, CF, CPWM, NONFAULT, COMM, PWMA, PWMD, EN, VDD, and GL pins GH, FS, and SH machine model: all pins -250 +250 V -2 +2 kV Parameter voltage on pin NONFAULT voltage on pin VFB voltage on pin IFB continuous t < 1 ms continuous t < 1 ms Conditions Min -0.1 -0.1 -0.1 -5 -9 Max +5 +5 +9 +5 +9 Unit V V V V V
-1
+1
kV
10. Thermal characteristics
Table 5. Symbol Rth(j-a) Thermal characteristics Parameter thermal resistance from junction to ambient Conditions in free air; SO24 package in free air; SSOP24 package Typ 80 111 Unit K/W K/W
11. Characteristics
Table 6. Characteristics Tamb = 25 C; VVDD = 12 V; RIREF = 33 k; VEN = VVDD and CPWM connected to a capacitor, unless otherwise specified. All voltages are measured with respect to signal ground (SGND, pin 10). SGND and PGND connected together. GL, GH, COMM, NONFAULT and PWMD pins left open (unless otherwise specified). Currents are positive when flowing into the IC. Parameters valid for all types (unless otherwise specified). Symbol High voltage Ileak Start-up Vstartup(VDD) Vstop(VDD) Vhys(VDD) Istartup(VDD) VDD start-up voltage stop voltage on pin VDD hysteresis voltage on pin VDD start-up current on pin VDD UBA2071T and UBA2071TS UBA2071AT and UBA2071ATS VVDD = 11 V; EN pin grounded UBA2071T and UBA2071TS UBA2071AT and UBA2071ATS 11.7 10.5 9.8 1.8 0.6 0.13 12.1 10.9 10.1 2 0.8 0.16 12.5 11.3 10.4 2.2 1.0 0.19 V V V V V mA leakage current VFS, VGH, and VSH = 630 V; VVDD = 0 V 2 A Parameter Conditions Min Typ Max Unit
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
24 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
Table 6. Characteristics ...continued Tamb = 25 C; VVDD = 12 V; RIREF = 33 k; VEN = VVDD and CPWM connected to a capacitor, unless otherwise specified. All voltages are measured with respect to signal ground (SGND, pin 10). SGND and PGND connected together. GL, GH, COMM, NONFAULT and PWMD pins left open (unless otherwise specified). Currents are positive when flowing into the IC. Parameters valid for all types (unless otherwise specified). Symbol Vclamp(VDD) Parameter clamp voltage on pin VDD Conditions EN pin grounded; IVDD = 0.22 mA; UBA2071T and UBA2071TS EN pin grounded; IVDD = 3 mA; UBA2071T and UBA2071TS IVDD Ignition fsw(max)/fsw(min) maximum switching frequency to minimum switching frequency ratio maximum voltage on pin CVFB charge current on pin CVFB lamp on detection threshold voltage on pin IFB current on pin VDD oscillating at fsw(min); CCF = 100 pF disabled; VVDD = 11 V oscillating; CF = 100 pF; GL and GH open fsw(min) Vref(creg) VIFB(min) VIFB(max) Ri(IFB) gm(OTA) Drivers Isource(drv) Rsink(drv) tno VFd(bs) PWM dimming IVDD td(en)PWM
UBA2071_A_1
Min 13 -
Typ
Max
Unit V V mA
13.35 13.7 14.0 0.22
current on pin VDD
EN pin grounded; VVDD = 14.0 V; UBA2071AT and UBA2071ATS
2.2
2.4
2.6
kHz
VCVFB(max) Ich(CVFB) Vth(lod)(IFB) Normal operation IVDD
VVFB = 2 V; VCVFB(max) = 2 V -24 0.9
2.5 -21 1.05
-18 1.2
V A V
1.2 [1][2] [1][2]
1.5 0.16 1.5 40 1.26 -2.5 2.5 45 24 16.5 -90 16.0 1.3 1.5
1.8 100 42 1.32 19 -75 18.5 1.5 2.0
mA mA mA kHz kHz V V V k k A/V mA s V
minimum switching frequency current regulation reference voltage minimum voltage on pin IFB maximum voltage on pin IFB input resistance on pin IFB OTA transconductance driver source current driver sink resistance non-overlap time bootstrap diode forward voltage current on pin VDD PWM enable delay time
CCF = 100 pF
10 38 1.20
for linear operating range for linear operating range VIFB = 1 V VIFB = -1 V
14
VGL, VGH = 4 V; VVDD = VFS = 12 V VGL, VGH = 2 V; VVDD = VFS = 12 V IFS = 5 mA
-105 13.5 1.1 1.0
CCF = 100 pF; VPWMD = H; VCSWP = 0 V
1.0 3
1.2 4
1.4 5
mA ms
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
25 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
Table 6. Characteristics ...continued Tamb = 25 C; VVDD = 12 V; RIREF = 33 k; VEN = VVDD and CPWM connected to a capacitor, unless otherwise specified. All voltages are measured with respect to signal ground (SGND, pin 10). SGND and PGND connected together. GL, GH, COMM, NONFAULT and PWMD pins left open (unless otherwise specified). Currents are positive when flowing into the IC. Parameters valid for all types (unless otherwise specified). Symbol fPWM Ich(CSWP) Idch(CSWP) Ri(PWMA) Vi(PWMA) PWM(min) PWM(max) PWMD Isource(PWMD) Isink(PWMD) Vth(H)(PWMD) Vth(L)(PWMD) Parameter PWM frequency CCPWM = 33 nF charge current on pin CSWP discharge current on pin CSWP input resistance on pin PWMA input voltage on pin PWMA minimum PWM duty cycle CPWM pin connected to SGND maximum PWM duty cycle duty cycle on pin PWMD source current on pin PWMD sink current on pin PWMD HIGH-level threshold voltage on pin PWMD LOW-level threshold voltage on pin PWMD clock LOW-level voltage on pin ICOMM = 10 A COMM clock LOW-level current on pin COMM VCOMM = 1.5 V VPWMD = 3 V VPWMD = 1 V for minimum PWM duty cycle for maximum PWM duty cycle
[3] [3] [3] [3]
Conditions
[1]
Min 75 306 -23 17 80 12 0.85
Typ 324 -20 20 100 1.24 3 12 0 100 0.6 1.2 -
Max 1000 342 -17 23 120 100 1.7 -
Unit Hz Hz A A k V V % % % % mA mA V V
PWMD low; VCSWP = 1 V PWMD high; VCSWP = 1 V
Communication (COMM pin) VL(clk)(COMM) IL(clk)(COMM) VH(clk)(COMM) IH(clk)(COMM) VO(hbswoff)(COMM) Ith(det)hsw(COMM) 0 4 -120 0.1 5.0 4.3 -4.5 12 -100 0.2 4.6 -80 V mA V mA V A
clock HIGH-level voltage on pin ICOMM = -10 A COMM clock HIGH-level current on pin VCOMM = 2.5 V COMM half bridge switch-off output voltage on pin COMM hard switching detection threshold current on pin COMM open/short protection threshold voltage on pin VFB overvoltage threshold voltage on pin VFB input resistance on pin VFB discharge current on pin CVFB VVFB < Vth(osp)(VFB) or VVFB > Vth(ov)(VFB); VCVFB = 2 V overvoltage extra threshold voltage on pin VFB
Rev. 01 -- 23 June 2008
PWMD = 5 V Clock = high; PWMD = low
Protections Vth(osp)(VFB) Vth(ov)(VFB) Ri(VFB) Idch(CVFB) Vth(ovextra)(VFB)
UBA2071_A_1
50 2.40 500 17 2.9
100 2.50 670 20 3.0
150 2.60 840 23 3.1
mV V k A V
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
26 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
Table 6. Characteristics ...continued Tamb = 25 C; VVDD = 12 V; RIREF = 33 k; VEN = VVDD and CPWM connected to a capacitor, unless otherwise specified. All voltages are measured with respect to signal ground (SGND, pin 10). SGND and PGND connected together. GL, GH, COMM, NONFAULT and PWMD pins left open (unless otherwise specified). Currents are positive when flowing into the IC. Parameters valid for all types (unless otherwise specified). Symbol Vth(osp)(IFB) Vth(ocd)(IFB) Vth(hsw)(SH) Idch(CVFB) Vth(det)arc(IFB) tspike(min) td(o)fault tto(fault) Voc(NONFAULT) Vtrig(I)NONFAULT Itrig(I)NONFAULT INONFAULT Isc(NONFAULT) Isink(NONFAULT) Enable (EN pin) Vth(H)2(EN) Vth(H)1(EN) Vth(L)(EN) Ibias(EN)
[1] [2] [3]
Parameter open/short protection threshold voltage on pin IFB overcurrent detection threshold voltage on pin IFB hard switching threshold voltage on pin SH
Conditions
Min 200 2.65 36 -
Typ 250 3.0 56 41 5 200 1.00 5.0 4.3 -27 -195 -220 1 2.76 5
Max 300 3.3 46 1.15 5.3 4.8 -22 -160 -180 1.3 2.87 1.7
Unit mV V V A V ns s V V A A A mA V V V A
discharge current on pin CVFB hard switching detected; VCVFB = 2 V arc detection threshold voltage on pin IFB minimum spike time fault output delay time fault time-out time open-circuit voltage on pin NONFAULT input trigger voltage on pin NONFAULT input trigger current on pin NONFAULT current on pin NONFAULT short circuit current on pin NONFAULT VNONFAULT = 3 V VNONFAULT = 0 V to active arcing protection CCT = 100 nF CCT = 100 nF
0.85 4.7 3.8 -32 -230 -260 0.7 2.65 0.9
0.063 0.069 0.075 s
sink current on pin NONFAULT VNONFAULT = 1 V HIGH-level threshold voltage 2 on pin EN HIGH-level threshold voltage 1 on pin EN LOW-level threshold voltage on pin EN bias current on pin EN
Given frequency is switching frequency of GL and GH. Sawtooth frequency on CF pin is twice as high. Can be set by external capacitor PWMD is active low: A low level on the PWMD pin corresponds with lamps-on. Example: PWM = 20 % means PWMD is low during 20 % of each cycle and the lamps are on 20 % of the time, resulting in a light output of 20 %.
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
27 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
12. Application information
Figure 19 shows an example backlighting configuration, where the inverter is supplied from a high voltage DC source and the IC is supplied by means of a V/t supply (C14, C15, Z1 and D1). Two lamps are connected, each to the output of its own transformer. The leakage inductance of this transformer provides the ballast impedance for the lamps. An analog voltage is converted to a PWM signal to provide for the desired brightness level. Lamp short detection is done via the lamp voltage sensing, D13 and D23, and the NONFAULT pin. Figure 20 shows an example of a balanced application using one UBA2071 and one UBA2073.
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
28 of 35
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Product data sheet Rev. 01 -- 23 June 2008
(c) NXP B.V. 2008. All rights reserved. UBA2071_A_1
NXP Semiconductors
R2 R4
C1 (1) D1
HVDC NONFAULT GND
C2
C15
Z1
VDD EN
NONFAULT
GH FS
C9
Q1
C14 CCFL 1
CN1
EN PWMA PWMD
C3
C10
CIFB SH
C11 D11
D13
C4 CVFB C5 C6
CT CF
C12 D12 R11 C13
D14
UBA2071
GL
Q2 T1 CCFL 2
C7 CSWP R1
IREF SGND
D23 C21 D21 D24 C22 D22 R21 C23
C8 CPWM
PWMA PWMD COMM VFB IFB PGND
Half bridge control IC for CCFL backlighting
UBA2071; UBA2071A
R3 R5
R6
014aaa115
(1) Optional lamp short protection is available via the NONFAULT pin.
Fig 19. Example of single IC backlighting application
29 of 35
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Product data sheet Rev. 01 -- 23 June 2008
(c) NXP B.V. 2008. All rights reserved. UBA2071_A_1
NXP Semiconductors
HVsupply
UBA2071
VDD IREF CF CT CSWP CVFB CIFB CPWM SGND PWMA enable PWMD PWMA EN PWMD GL PGND IFB VFB COMM NONFAULT GH SH FS
UBA2073
GH SH FS VDD
GL PGND COMM
Half bridge control IC for CCFL backlighting
UBA2071; UBA2071A
014aaa116
Fig 20. Example of balanced backlighting application
30 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
13. Package outline
SO24: plastic small outline package; 24 leads; body width 7.5 mm SOT137-1
D
E
A X
c y HE vMA
Z 24 13
Q A2 A1 pin 1 index Lp L 1 e bp 12 wM detail X (A 3) A
0
5 scale
10 mm
DIMENSIONS (inch dimensions are derived from the original mm dimensions) UNIT mm inches A max. 2.65 0.1 A1 0.3 0.1 A2 2.45 2.25 A3 0.25 0.01 bp 0.49 0.36 c 0.32 0.23 D (1) 15.6 15.2 0.61 0.60 E (1) 7.6 7.4 0.30 0.29 e 1.27 0.05 HE 10.65 10.00 L 1.4 Lp 1.1 0.4 Q 1.1 1.0 0.043 0.039 v 0.25 0.01 w 0.25 0.01 y 0.1 Z
(1)
0.9 0.4
0.012 0.096 0.004 0.089
0.019 0.013 0.014 0.009
0.419 0.043 0.055 0.394 0.016
0.035 0.004 0.016
8 o 0
o
Note 1. Plastic or metal protrusions of 0.15 mm (0.006 inch) maximum per side are not included. OUTLINE VERSION SOT137-1 REFERENCES IEC 075E05 JEDEC MS-013 JEITA EUROPEAN PROJECTION
ISSUE DATE 99-12-27 03-02-19
Fig 21. Package outline SOT137-1 (SO24)
UBA2071_A_1 (c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
31 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
SSOP24: plastic shrink small outline package; 24 leads; body width 5.3 mm
SOT340-1
D
E
A X
c y HE vMA
Z 24 13
Q A2 pin 1 index A1 (A 3) Lp L 1 e bp 12 wM detail X A
0
2.5 scale
5 mm
DIMENSIONS (mm are the original dimensions) UNIT mm A max. 2 A1 0.21 0.05 A2 1.80 1.65 A3 0.25 bp 0.38 0.25 c 0.20 0.09 D (1) 8.4 8.0 E (1) 5.4 5.2 e 0.65 HE 7.9 7.6 L 1.25 Lp 1.03 0.63 Q 0.9 0.7 v 0.2 w 0.13 y 0.1 Z (1) 0.8 0.4 8 o 0
o
Note 1. Plastic or metal protrusions of 0.2 mm maximum per side are not included. OUTLINE VERSION SOT340-1 REFERENCES IEC JEDEC MO-150 JEITA EUROPEAN PROJECTION
ISSUE DATE 99-12-27 03-02-19
Fig 22. Package outline SOT340 (SSOP24)
UBA2071_A_1 (c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
32 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
14. Revision history
Table 7. Revision history Release date 20080623 Data sheet status Product data sheet Change notice Order number Supersedes Document ID UBA2071_A_1
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
33 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
15. Legal information
15.1 Data sheet status
Document status[1][2] Objective [short] data sheet Preliminary [short] data sheet Product [short] data sheet
[1] [2] [3]
Product status[3] Development Qualification Production
Definition This document contains data from the objective specification for product development. This document contains data from the preliminary specification. This document contains the product specification.
Please consult the most recently issued document before initiating or completing a design. The term `short data sheet' is explained in section "Definitions". The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status information is available on the Internet at URL http://www.nxp.com.
15.2 Definitions
Draft -- The document is a draft version only. The content is still under internal review and subject to formal approval, which may result in modifications or additions. NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information. Short data sheet -- A short data sheet is an extract from a full data sheet with the same product type number(s) and title. A short data sheet is intended for quick reference only and should not be relied upon to contain detailed and full information. For detailed and full information see the relevant full data sheet, which is available on request via the local NXP Semiconductors sales office. In case of any inconsistency or conflict with the short data sheet, the full data sheet shall prevail.
damage. NXP Semiconductors accepts no liability for inclusion and/or use of NXP Semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer's own risk. Applications -- Applications that are described herein for any of these products are for illustrative purposes only. NXP Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Quick reference data -- The Quick reference data is an extract of the product data given in the Limiting values and Characteristics sections of this document, and as such is not complete, exhaustive or legally binding. Limiting values -- Stress above one or more limiting values (as defined in the Absolute Maximum Ratings System of IEC 60134) may cause permanent damage to the device. Limiting values are stress ratings only and operation of the device at these or any other conditions above those given in the Characteristics sections of this document is not implied. Exposure to limiting values for extended periods may affect device reliability. Terms and conditions of sale -- NXP Semiconductors products are sold subject to the general terms and conditions of commercial sale, as published at http://www.nxp.com/profile/terms, including those pertaining to warranty, intellectual property rights infringement and limitation of liability, unless explicitly otherwise agreed to in writing by NXP Semiconductors. In case of any inconsistency or conflict between information in this document and such terms and conditions, the latter will prevail. No offer to sell or license -- Nothing in this document may be interpreted or construed as an offer to sell products that is open for acceptance or the grant, conveyance or implication of any license under any copyrights, patents or other industrial or intellectual property rights.
15.3 Disclaimers
General -- Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. Right to make changes -- NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. This document supersedes and replaces all information supplied prior to the publication hereof. Suitability for use -- NXP Semiconductors products are not designed, authorized or warranted to be suitable for use in medical, military, aircraft, space or life support equipment, nor in applications where failure or malfunction of an NXP Semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental
15.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners.
16. Contact information
For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com
UBA2071_A_1
(c) NXP B.V. 2008. All rights reserved.
Product data sheet
Rev. 01 -- 23 June 2008
34 of 35
NXP Semiconductors
UBA2071; UBA2071A
Half bridge control IC for CCFL backlighting
17. Contents
1 2 3 4 5 6 7 7.1 7.2 8 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12 8.13 8.14 8.14.1 8.14.2 8.14.3 8.14.4 8.14.5 8.14.6 8.14.7 8.14.8 8.14.9 8.14.10 9 10 11 12 13 14 15 15.1 15.2 15.3 General description . . . . . . . . . . . . . . . . . . . . . . 1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Quick reference data . . . . . . . . . . . . . . . . . . . . . 2 Ordering information . . . . . . . . . . . . . . . . . . . . . 3 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Pinning information . . . . . . . . . . . . . . . . . . . . . . 5 Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 5 Functional description . . . . . . . . . . . . . . . . . . . 6 Supply, Start-up and UnderVoltage LockOut (UVLO) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 VDD clamp. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Enable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 The oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Non-overlap . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Low-side and high-side drivers . . . . . . . . . . . . . 9 DC blocking capacitor charging . . . . . . . . . . . . 9 Lamp (re-)ignition . . . . . . . . . . . . . . . . . . . . . . 11 Overvoltage control. . . . . . . . . . . . . . . . . . . . . 13 Lamp current control. . . . . . . . . . . . . . . . . . . . 14 PWM dimming . . . . . . . . . . . . . . . . . . . . . . . . 15 The fault timer. . . . . . . . . . . . . . . . . . . . . . . . . 17 Communication. . . . . . . . . . . . . . . . . . . . . . . . 18 Protections . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Voltage feedback open or short protection . . . 19 Overvoltage protection . . . . . . . . . . . . . . . . . . 20 Hard switching protection . . . . . . . . . . . . . . . . 20 Overvoltage extra protection. . . . . . . . . . . . . . 20 Current feedback open or short protection . . . 21 Overcurrent detection . . . . . . . . . . . . . . . . . . . 21 Arcing detection . . . . . . . . . . . . . . . . . . . . . . . 21 Ignition Failure (IF) . . . . . . . . . . . . . . . . . . . . . 22 The NONFAULT pin . . . . . . . . . . . . . . . . . . . . 22 Fault input via the COMM pin . . . . . . . . . . . . . 23 Limiting values. . . . . . . . . . . . . . . . . . . . . . . . . 23 Thermal characteristics. . . . . . . . . . . . . . . . . . 24 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 24 Application information. . . . . . . . . . . . . . . . . . 28 Package outline . . . . . . . . . . . . . . . . . . . . . . . . 31 Revision history . . . . . . . . . . . . . . . . . . . . . . . . 33 Legal information. . . . . . . . . . . . . . . . . . . . . . . 34 Data sheet status . . . . . . . . . . . . . . . . . . . . . . 34 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 15.4 16 17 Trademarks . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Contact information . . . . . . . . . . . . . . . . . . . . 34 Contents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Please be aware that important notices concerning this document and the product(s) described herein, have been included in section `Legal information'.
(c) NXP B.V. 2008.
All rights reserved.
For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com Date of release: 23 June 2008 Document identifier: UBA2071_A_1

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