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DS3992-DS3992Z-09N+-DS3992Z-09P+-DS3992Z-18N+
Two-Channel, Push-Pull CCFL Controller
General DescriptionThe DS3992 is a low-cost, two-channel controller for
cold-cathode fluorescent lamps (CCFLs) that are used
to backlight liquid crystal displays (LCDs). The DS3992
can drive multiple CCFLs per channel, making it ideal
for 4- and 6-lamp LCD PC monitor and TV applications.
The DS3992 uses a push-pull drive scheme to convert a
DC voltage (5V to 24V) to the high voltage (300VRMSto
1400VRMS) AC waveform that is required to power the
CCFLs. The push-pull drive scheme uses a minimal
number of external components, which reduces compo-
nent and assembly cost and makes the printed circuit
board (PC board) design easy to implement. The push-
pull drive scheme also provides an efficient DC-to-AC
conversion and produces near-sinusoidal waveforms.
ApplicationsLCD PC Monitors
LCD-TVs
FeaturesTwo-Channel CCFL Controller for Backlighting
LCD Panels for PC Monitors and LCD-TVsMinimal BOM Provides Low-Cost Inverter SolutionPer-Channel Lamp Fault Monitoring for Lamp-
Open, Lamp Overcurrent, Failure to Strike, and
Overvoltage ConditionsAccurate (±10%) On-Board Oscillator for LampFrequency (40kHz to 80kHz)Accurate (±10%) On-Board Oscillator for DPWMBurst-Dimming Frequency (90Hz to 220Hz or
180Hz to 440Hz)Device Supply Undervoltage LockoutInverter Supply Undervoltage LockoutBurst-Dimming Soft-Start Minimizes Audible
Transformer NoiseStrike Frequency Boost100% to < 10% Dimming Range4.5V to 5.5V Single-Supply Operation-40°C to +85°C Temperature Range16-Pin SO Package (150 mils)
DS3992wo-Channel, Push-Pull CCFL Controller
SO-150TOP VIEW
OVD2
LCM1
OVD1
GA2
VCC
VCC
GA1
GB1
POSC
LOSC
GB2
VCC
GND
SVM
BRIGHT
LCM2
DS3992
Pin ConfigurationRev 0; 9/06
+Denotes lead-free package.
T&R denotes tape-and-reel package.
Ordering Information
PARTTEMP RANGEDIMMING
FREQUENCY RANGEBRIGHT POLARITYPIN-PACKAGEDS3992Z-09P+-40°C to +85°C90Hz to 220HzPositive16 SO-16 (150 mils)
DS3992Z-09N+-40°C to +85°C90Hz to 220HzNegative16 SO-16 (150 mils)
DS3992Z-18P+-40°C to +85°C180Hz to 440HzPositive16 SO-16 (150 mils)
DS3992Z-18N+-40°C to +85°C180Hz to 440HzNegative16 SO-16 (150 mils)
DS3992Z-09P+T&R-40°C to +85°C90Hz to 220HzPositive16 SO-16 (150 mils)
DS3992Z-09N+T&R-40°C to +85°C90Hz to 220HzNegative16 SO-16 (150 mils)
DS3992Z-18P+T&R-40°C to +85°C180Hz to 440HzPositive16 SO-16 (150 mils)
DS3992Z-18N+T&R-40°C to +85°C180Hz to 440HzNegative16 SO-16 (150 mils)
Typical Operating Circuits appear at end of data sheet.
DS3992wo-Channel, Push-Pull CCFL Controller
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED OPERATING CONDITIONS(TA= -40°C to +85°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Voltage on VCCRelative to Ground.......................-0.5V to +6.0V
Voltage on Any Leads Other
Than VCC..............0.5V to (VCC+ 0.5V), not to exceed +6.0V
Operating Temperature Range...........................-40°C to +85°C
Storage Temperature Range.............................-55°C to +125°C
Soldering Temperature...................See J-STD-020 Specification
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSSupply VoltageVCC(Note 1)4.55.5V
SVM Voltage RangeVSVM-0.3VCC +
0.3V
BRIGHT Voltage RangeVBRIGHT-0.3VCC +
0.3V
LCM Voltage RangeVLCM(Note 2)-0.3VCC +
0.3V
OVD Voltage RangeVOVD(Note 2)-0.3VCC +
0.3V
Gate-Driver Output Charge LoadingQG20nC
ELECTRICAL CHARACTERISTICS(VCC= +4.5V to +5.5V, TA= -40°C to +85°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSSupply CurrentICCGA, GB loaded with 600pF, 2 channels
active816mA
Low-Level Output Voltage (GA, GB)VOLIOL = 4mA0.4V
High-Level Output Voltage (GA, GB)VOH1IOH1 = -1mAVCC -
0.4V
UVLO Threshold: VCC RisingVUVLOR4.3V
UVLO Threshold: VCC FallingVUVLOF3.7V
UVLO HysteresisVUVLOH100mV
SVM Falling-Edge ThresholdVSVM1.92.02.1V
SVM HysteresisVSVMH150mV
LCM and OVD DC Bias VoltageVDCB1.35V
LCM and OVD Input ResistanceRDCB50kΩ
Lamp-Off ThresholdVLOT(Note 3)1.651.751.85V
Lamp Over CurrentVLOC(Note 3)3.153.353.55V
Lamp Regulation ThresholdVLRT(Note 3)2.252.352.45V
OVD ThresholdVOVDT(Note 3)2.252.352.45V
Lamp Frequency RangefLFS:OSC4080kHz
DS3992wo-Channel, Push-Pull CCFL Controller
Note 1:All voltages are referenced to ground unless otherwise noted. Currents into the I.C. are positive, out of the I.C. negative.
Note 2:During fault conditions, the AC-coupled feedback values are allowed to be below the Absolute Maximum Rating of the LCM or
OVD pin for up to 1s.
Note 3:Voltage with respect to VDCB.
ELECTRICAL CHARACTERISTICS (continued)(VCC= +4.5V to +5.5V, TA= -40°C to +85°C.)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSLamp Frequency TolerancefLFS:TOLLOSC resistor ±2% over temperature-10+10%
DS3992Z-09P/N90220DPWM Frequency RangefDSR:OSCDS3992Z-18P/N180440Hz
DPWM Frequency TolerancefDSR:TOLPOSC resistor ±2% over temperature-10+10%
DS3992Z-09P / DS3992Z-18P0.5BRIGHT Voltage:
Minimum BrightnessVBMINDS3992Z-09N / DS3992Z-18N2.0V
DS3992Z-09P / DS3992Z-18P2.0BRIGHT Voltage:
Maximum BrightnessVBMAXDS3992Z-09N / DS3992Z-18N0.5V
Gate-Driver Output Rise/Fall TimetR / tFCL = 600pF50100ns
GAn and GBn Duty Cycle44%
Strike TimetSTRIKE500ms
Typical Operating Characteristics(VCC= 5.0V, TA= +25°C, unless otherwise noted.)
ACTIVE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
DS3992 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
DPWM = 10%
DPWM = 50%
DPWM = 100%
SVM ≤ 2V
GATE QC = 3.5nC
fLFOSC = 64kHz
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE
DS3992 toc02
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
VCC = 5.5V
GATE QC = 3.5nC
fLFOSC = 64kHz
DPWM = 100%
VCC = 5.0V
VCC = 4.5V
INTERNAL FREQUENCY CHANGE
vs. TEMPERATURE
DS3992 toc03
TEMPERATURE (°C)
FREQUENCY CHANGE (%)
DPWM
FREQUENCY
LAMP
FREQUENCY
DS3992wo-Channel, Push-Pull CCFL Controller
Typical Operating Characteristics (continued)(VCC= 5.0V, TA= +25°C, unless otherwise noted.)
TYPICAL OPERATION AT 16VDS3992 toc0410μs
5.0V GA
10μs
5.0V GB
10μs
2.0V LCM
10μs
2.0V OVD
BURST DIMMING AT 150Hz AND 10%DS3992 toc051ms
5.0V GA
1ms
5.0V GB
1ms
2.0V LCM
1ms
2.0V OVD
TYPICAL STARTUP WITH SVMDS3992 toc062ms
2.0V SVM
2ms
5.0V GB
2ms
2.0V LCM
2ms
2.0V OVD
BURST DIMMING AT 150Hz AND 50%DS3992 toc071ms
5.0V GA
1ms
5.0V GB
1ms
2.0V LCM
1ms
2.0V OVD
SOFT-START AT VINV = 16VDS3984 toc0850μs
5.0V GA
50μs
5.0V GB
50μs
2.0V LCM
50μs
2.0V OVD
LAMP STRIKE—EXPANDED VIEWDS3992 toc091ms
5.0V GA
1ms
5.0V GB
1ms
2.0V LCM
1ms
2.0V OVD
LAMP OUT (LAMP OPENED),
AUTORETRY DISABLED DS3992 toc100.25
5.0V GA
5.0V GB
2.00V LCM
2.00V OVD
LAMP OPENED
DS3992wo-Channel, Push-Pull CCFL Controller
Pin Description
PIN
NUMBERNAMEI/OFUNCTIONLOSC⎯
Lamp Oscillator Resistor Adjust. A resistor (RLOSC) to ground on this pin sets the frequency ofthe lamp oscillator (fLFS:OSC). [RLOSC x fLFS:OSC = 1.6E9].POSC⎯
Burst Dimming DPWM Oscillator Resistor Adjust. A resistor (RPOSC) to ground on this leadsets the frequency (fDSR:OSC) of the burst-dimming DPWM oscillator. [RPOSC x fDSR:OSC = 4.0E6
for DS3992Z-09P and DS3992Z-09N and RPOSC x fDSR:OSC = 8.0E6 for DS3992Z-18P and
DS3992Z-18N].BRIGHTI
Lamp Brightness Control. An analog voltage at this input controls the lamp brightness. SeeTable 1 for details.SVMI
Supply Voltage Monitor. The DC inverter supply voltage is monitored by an external resistordivider. The resistor-divider should be set such that it provides 2V at this pin for the minimum
allowable range of the DC inverter supply. Pulling this input below 2V will turn the lamps off and
reset the controller. Connect to VCC if not used.GA1O
MOSFET Gate Drive A for Channel 1. Connect directly to the gate of a logic-level moden-channel MOSFET.GB1O
MOSFET Gate Drive B for Channel 1. Connect directly to the gate of a logic-level moden-channel MOSFET.LCM1I
Lamp Current Monitor Input for Channel 1. Lamp current is monitored by a resistor placed inseries with the low-voltage side of the lamp.OVD1I
Over Voltage Detection for Channel 1. Lamp voltage is monitored by a capacitor dividerplaced on the high-voltage side of the lamp.GND⎯
Signal GroundVCC⎯
Supply. 4.5V to 5.5V.GA2O
MOSFET Gate Drive A for Channel 2. Connect directly to the gate of a logic-level moden-channel MOSFET.GB2O
MOSFET Gate Drive B for Channel 2. Connect directly to the gate of a logic-level moden-channel MOSFET.LCM2I
Lamp Current Monitor Input for Channel 2. Lamp current is monitored by a resistor placed inseries with the low-voltage side of the lamp.OVD2I
Overvoltage Detection for Channel 2. Lamp voltage is monitored by a capacitor dividerplaced on the high-voltage side of the lamp.VCC⎯
Supply. 4.5V to 5.5V.VCC⎯
Supply. 4.5V to 5.5V.
DS3992wo-Channel, Push-Pull CCFL Controller
GAn
GBn
OVDn
OVERVOLTAGE
DETECTION
LCMn
LAMP CURRENT
MONITOR
[20.48MHz TO 40.96MHz]
90Hz TO 220Hz OR
180Hz TO 440Hz
EXTERNAL
RESISTOR LAMP
FREQUENCY SET
VCC
[4.5V TO 5.5V]
GND
TWO
INDEPENDENT
CCFL
CONTROLLERS
(SEE FIGURE 2)
EXTERNAL
RESISTOR DPWM
FREQUENCY SET
ANALOG
BRIGHTNESS
CONTROL
SVM
SUPPLY VOLTAGE
MONITOR
[40kHz TO 80kHz]
CHANNEL FAULT
CHANNEL ENABLE
MOSFET
GATE DRIVERS
LOSC
BRIGHT
POSCDPWM
SIGNAL
2.0V
40kHz TO 80kHz
OSCILLATOR (±10%)
90Hz TO 220Hz OR
180Hz TO 440Hz
OSCILLATOR (±10%)
RAMP
GENERATOR
x512
PLL
FAULT
HANDLING
SYSTEM
ENABLE /
POR
VREF
UVLO
DS3992
Functional Diagrams
Figure 1. DS3992 Functional Diagram
Detailed Description
Each DS3992 channel drives two logic-level n-channel
MOSFETs that are connected between the ends of
a step-up transformer and ground (See the Typical
Operating Circuits). The transformer has a center tap
on the primary side that is connected to the DC inverter
voltage supply. The DS3992 alternately turns on the two
MOSFETs to create the high-voltage AC waveform on
the secondary side. By varying the duration of the
MOSFET turn-on times, the DS3992 is able to accurate-
ly control the CCFL current.
A resistor in series with the CCFL’s ground connection
enables current monitoring. The voltage across this
resistor is fed to the lamp current monitor (LCM) input
and compared to an internal reference voltage to deter-
mine the duty cycle for the MOSFET gates.
The DS3992 supports a 1 lamp per channel configura-
tion with fully independent lamp control and minimal
external components. The DS3992 is also capable of
controlling more than 1 lamp per channel using a
wired-OR feedback circuit. See the Typical Operating
Circuitssection for more information.
Block diagrams of the DS3992 are shown in Figures 1
and 2. More operating details of the DS3992 are dis-
cussed on the following pages of this data sheet.
Dimming Control
The DS3992 uses “burst” dimming to control the lamp
brightness. An analog voltage applied at the BRIGHT
input pin determines the duty cycle of a digital pulse-
width-modulated (DPWM) signal (90Hz to 220Hz for
DS3992Z-09P/DS3992Z-09N and 180Hz to 440Hz for
DS3992Z-18P/DS3992Z-18N). During the high period of
the DPWM cycle, the lamp is driven at the selected
lamp frequency (40kHz to 80kHz) as shown in Figure 3.
This part of the cycle is also called the “burst” period
because of the lamp frequency burst that occurs
DS3992wo-Channel, Push-Pull CCFL Controller
Functional Diagrams (continued)
GATE
DRIVERS
GAn
GBn
DIGITAL
CCFL
CONTROLLER
CHANNEL FAULT
512 x LAMP FREQUENCY
[20.48MHz TO 40.96MHz]
LAMP FREQUENCY
[40kHz TO 80kHz]
DIMMING PWM SIGNAL
CHANNEL ENABLE
MOSFET
GATE
DRIVERS
LCMn
LAMP CURRENT MONITOR
400mV
2.0V
LAMP OVERCURRENT
LAMP STRIKE AND REGULATION
LAMP OUT
1.0V
1.0V
OVDn
OVERVOLTAGE DETECTOR
LAMP MAXIMUM VOLTAGE REGULATION
64 LAMP CYCLE
INTEGRATOR
OVERVOLTAGE
Figure 2. DS3992 Per Channel Logic Diagram
90Hz TO 220Hz
180Hz TO 440Hz
LAMP CURRENT
DPWM SIGNAL
Figure 3. Digital-PWM Dimming and Soft-Start
