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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

n Suitable for operating in a very wide inverter supply voltage range (up to 550 V DC).

n Integrated level shifter.

n Integrated bootstrap diode.

n Lamp current control by means of a true zero voltage switching resonant control

principle.

n Sample & Hold circuit, maintaining current control value during PWM lamp-off

situation.

n Separately deﬁnable time constants for current control loop and PWM dimming

attack/decay setting.

n Overvoltage control.

n Overcurrent protection.

n Ignition failure detection.

n Hard switching control.

n Arcing detection.

n Open/short pin protections on feedback pins.

n Integrated, programmable fault timer.

UBA2071; UBA2071A

Half bridge control IC for CCFL backlighting

Rev. 01 — 23 June 2008 Product data sheet

Summary of content (35 pages)

PAGE 1
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.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting n Bidirectional pin acting both as fault signaling output and input, allowing external fault interfacing to operate via the integrated fault timer. n Brightness level adjustment through PWM dimming. n Integrated PWM generator. n Power-down mode. n Communication pin for master / slave operation. n DC blocking capacitor pre-charging sequence. n Supply clamp (UBA2071 only). 3.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting Table 1. Quick reference data. Tamb = 25 °C; VVDD = 12 V; RIREF = 33 kΩ; 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.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting 6.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting 7. Pinning information 7.1 Pinning IFB 1 24 GH CIFB 2 23 FS VFB 3 22 SH CVFB 4 21 n.c. CSWP 5 20 n.c. CT 6 CF 7 IREF 8 17 PGND CPWM 9 16 VDD UBA2071 19 n.c. 18 GL SGND 10 15 EN COMM 11 14 PWMA NONFAULT 12 13 PWMD 014aaa099 Fig 2. Pin assignment SO24 and SSOP24 package (top view) 7.2 Pin description Table 3.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting Table 3. Symbol Pin description …continued Description Function NONFAULT 12 Pin status signal input/output 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. PWMD digital PWM dimming input/output Digital output of internally generated PWM signal if a capacitor is connected to the CPWM pin.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting VHV UBA2071 FS CFS GH VDD SH QHS VHB GL LOAD 0.5 VHV QLS Cblock PGND 014aaa100 Fig 3. Basic half bridge inverter 8.1 Supply, Start-up and UnderVoltage LockOut (UVLO) start up current UBA2071 AUXILARY SUPPLY VDD C1 014aaa101 Fig 4. Supply configuration (for UBA2071 only) The UBA2071 is supplied via the VDD pin as shown in Figure 4.
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UBA2071; UBA2071A NXP Semiconductors 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.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting VCFH VCF 0 t VDD VGH − VSH 0 t VDD VGL 0 t VHV VHB 0 t tno 014aaa102 Fig 5. Oscillator, driver and half bridge voltages 8.
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UBA2071; UBA2071A NXP Semiconductors 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.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting (H)2(EN) EN (H)1(EN) (L)(EN) 0 GH GL VSH 0 0.5 T 7.5 T 3 / fsw(min) T 1 / fsw(max) disabled 7.5 T 3 / fsw(min) initial ignition sweep and normal mode DC blocking capacitor charging 014aaa252 Fig 7. DC blocking capacitor charging mode Remark: Due to the nature of the charging sequence, VCblock will automatically be charged to 0.5 × VHV (when given enough time).
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting Vlamp (V) (1) Vign (2) Vburn fsw(min) freg fign fsw(max) f (kHz) 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.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting ignition max fsw fign freg min 0 t ov Vsec 0 t VCVFB max VCVFB VCIFB VCSWP VCIFB VCSWP 0 t 0 t VPWMD nom Ilamp 0 initial ignition sweep PWM-enable delay t steady-state 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.
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UBA2071; UBA2071A NXP Semiconductors 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.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting Ich(CSWP) Idch(CSWP) to CCFLs OTA 0 IFB PWMD 1 S2 DSR S1 R1 Vref(creg) to VCO Ich(CVFB) UBA2071 CIFB CVFB C1 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.
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UBA2071; UBA2071A NXP Semiconductors 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.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting CPWM CPWM 9 9 C1 analog in PWMA 14 RPWMA PWMA 14 VPWMA(ref) PWM out PWM in PWMD 13 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.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting VCT 0 t VNONFAULT 0 t td(o)fault tto(fault) 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.
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UBA2071; UBA2071A NXP Semiconductors 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.
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UBA2071; UBA2071A NXP Semiconductors 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.
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UBA2071; UBA2071A NXP Semiconductors 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 µs for the overvoltage extra to react at all.
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UBA2071; UBA2071A NXP Semiconductors 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).
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UBA2071; UBA2071A NXP Semiconductors 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 NONFAULT from IC 014aaa114 Fig 18.
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UBA2071; UBA2071A NXP Semiconductors 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 Parameter VNONFAULT voltage on pin NONFAULT VVFB voltage on pin VFB voltage on pin IFB VIFB Conditions Min Max Unit −0.1 +5 V continuous −0.1 +5 V t < 1 ms −0.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting Table 6. Characteristics …continued Tamb = 25 °C; VVDD = 12 V; RIREF = 33 kΩ; 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.
PAGE 26
UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting Table 6. Characteristics …continued Tamb = 25 °C; VVDD = 12 V; RIREF = 33 kΩ; 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.
PAGE 27
UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting Table 6. Characteristics …continued Tamb = 25 °C; VVDD = 12 V; RIREF = 33 kΩ; 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.
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UBA2071; UBA2071A NXP Semiconductors 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.
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UBA2071; UBA2071A NXP Semiconductors 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 HE y v M A Z 24 13 Q A2 A (A 3) A1 pin 1 index θ Lp L 1 12 e detail X w M bp 0 5 10 mm scale DIMENSIONS (inch dimensions are derived from the original mm dimensions) UNIT A max. A1 A2 A3 bp c D (1) E (1) e HE L Lp Q v w y mm 2.65 0.3 0.1 2.45 2.25 0.25 0.49 0.36 0.32 0.23 15.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting SSOP24: plastic shrink small outline package; 24 leads; body width 5.3 mm D SOT340-1 E A X c HE y v M A Z 24 13 Q A2 A (A 3) A1 pin 1 index θ Lp L 1 12 w M bp e detail X 0 2.5 5 mm scale DIMENSIONS (mm are the original dimensions) UNIT A max. A1 A2 A3 bp c D (1) E (1) e HE L Lp Q v w y Z (1) θ mm 2 0.21 0.05 1.80 1.65 0.25 0.38 0.25 0.20 0.09 8.4 8.0 5.4 5.2 0.65 7.9 7.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting 14. Revision history Table 7. Revision history Document ID Release date Data sheet status Change notice Order number Supersedes UBA2071_A_1 20080623 Product data sheet - - - UBA2071_A_1 Product data sheet © NXP B.V. 2008. All rights reserved. Rev.
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UBA2071; UBA2071A NXP Semiconductors Half bridge control IC for CCFL backlighting 15. Legal information 15.1 Data sheet status Document status[1][2] Product status[3] Definition Objective [short] data sheet Development This document contains data from the objective specification for product development. Preliminary [short] data sheet Qualification This document contains data from the preliminary specification.
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UBA2071; UBA2071A NXP Semiconductors 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . .