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Rev 0; 9/06
Two-Channel, Push-Pull CCFL Controller
General Description
The 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 (300VRMS to 1400VRMS) AC waveform that is required to power the CCFLs. The push-pull drive scheme uses a minimal number of external components, which reduces component and assembly cost and makes the printed circuit board (PC board) design easy to implement. The pushpull drive scheme also provides an efficient DC-to-AC conversion and produces near-sinusoidal waveforms.
Features
o Two-Channel CCFL Controller for Backlighting LCD Panels for PC Monitors and LCD-TVs o Minimal BOM Provides Low-Cost Inverter Solution o Per-Channel Lamp Fault Monitoring for LampOpen, Lamp Overcurrent, Failure to Strike, and Overvoltage Conditions o Accurate (10%) On-Board Oscillator for Lamp Frequency (40kHz to 80kHz) o Accurate (10%) On-Board Oscillator for DPWM Burst-Dimming Frequency (90Hz to 220Hz or 180Hz to 440Hz) o Device Supply Undervoltage Lockout o Inverter Supply Undervoltage Lockout o Burst-Dimming Soft-Start Minimizes Audible Transformer Noise o Strike Frequency Boost o 100% to < 10% Dimming Range o 4.5V to 5.5V Single-Supply Operation o -40C to +85C Temperature Range o 16-Pin SO Package (150 mils)
DS3992
Applications
LCD PC Monitors LCD-TVs
Ordering Information
PART DS3992Z-09P+ DS3992Z-09N+ DS3992Z-18P+ DS3992Z-18N+ DS3992Z-09P+T&R DS3992Z-09N+T&R DS3992Z-18P+T&R DS3992Z-18N+T&R TEMP RANGE -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C DIMMING FREQUENCY RANGE 90Hz to 220Hz 90Hz to 220Hz 180Hz to 440Hz 180Hz to 440Hz 90Hz to 220Hz 90Hz to 220Hz 180Hz to 440Hz 180Hz to 440Hz BRIGHT POLARITY Positive Negative Positive Negative Positive Negative Positive Negative PIN-PACKAGE 16 SO-16 (150 mils) 16 SO-16 (150 mils) 16 SO-16 (150 mils) 16 SO-16 (150 mils) 16 SO-16 (150 mils) 16 SO-16 (150 mils) 16 SO-16 (150 mils) 16 SO-16 (150 mils)
+Denotes lead-free package. T&R denotes tape-and-reel package.
TOP VIEW
LOSC 1 POSC 2 BRIGHT 3
Pin Configuration
16 VCC 15 VCC 14 OVD2 13 LCM2
Typical Operating Circuits appear at end of data sheet.
SVM 4 GA1 5 GB1 6 LCM1 7 OVD1 8
DS3992
12 GB2 11 GA2 10 VCC 9 GND
SO-150
______________________________________________ Maxim Integrated Products
1
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Two-Channel, Push-Pull CCFL Controller DS3992
ABSOLUTE MAXIMUM RATINGS
Voltage on VCC Relative 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 ...........................-40C to +85C Storage Temperature Range .............................-55C to +125C Soldering Temperature...................See J-STD-020 Specification
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.
RECOMMENDED OPERATING CONDITIONS
(TA = -40C to +85C.)
PARAMETER Supply Voltage SVM Voltage Range BRIGHT Voltage Range LCM Voltage Range OVD Voltage Range Gate-Driver Output Charge Loading SYMBOL VCC VSVM VBRIGHT VLCM VOVD QG (Note 2) (Note 2) (Note 1) CONDITIONS MIN 4.5 -0.3 -0.3 -0.3 -0.3 TYP MAX 5.5 VCC + 0.3 VCC + 0.3 VCC + 0.3 VCC + 0.3 20 UNITS V V V V V nC
ELECTRICAL CHARACTERISTICS
(VCC = +4.5V to +5.5V, TA = -40C to +85C.)
PARAMETER Supply Current Low-Level Output Voltage (GA, GB) High-Level Output Voltage (GA, GB) UVLO Threshold: VCC Rising UVLO Threshold: VCC Falling UVLO Hysteresis SVM Falling-Edge Threshold SVM Hysteresis LCM and OVD DC Bias Voltage LCM and OVD Input Resistance Lamp-Off Threshold Lamp Over Current Lamp Regulation Threshold OVD Threshold Lamp Frequency Range SYMBOL ICC VOL VOH1 VUVLOR VUVLOF VUVLOH VSVM VSVMH VDCB RDCB VLOT VLOC VLRT VOVDT fLFS:OSC (Note 3) (Note 3) (Note 3) (Note 3) 1.65 3.15 2.25 2.25 40 1.9 3.7 100 2.0 150 1.35 50 1.75 3.35 2.35 2.35 1.85 3.55 2.45 2.45 80 2.1 CONDITIONS GA, GB loaded with 600pF, 2 channels active IOL = 4mA IOH1 = -1mA VCC 0.4 4.3 MIN TYP 8 MAX 16 0.4 UNITS mA V V V V mV V mV V k V V V V kHz
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Two-Channel, Push-Pull CCFL Controller
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +4.5V to +5.5V, TA = -40C to +85C.)
PARAMETER Lamp Frequency Tolerance DPWM Frequency Range DPWM Frequency Tolerance BRIGHT Voltage: Minimum Brightness BRIGHT Voltage: Maximum Brightness Gate-Driver Output Rise/Fall Time GAn and GBn Duty Cycle Strike Time tSTRIKE 500 SYMBOL fLFS:TOL fDSR:OSC fDSR:TOL VBMIN VBMAX tR / tF CONDITIONS LOSC resistor 2% over temperature DS3992Z-09P/N DS3992Z-18P/N POSC resistor 2% over temperature DS3992Z-09P / DS3992Z-18P DS3992Z-09N / DS3992Z-18N DS3992Z-09P / DS3992Z-18P DS3992Z-09N / DS3992Z-18N CL = 600pF 50 2.0 2.0 0.5 100 44 MIN -10 90 180 -10 TYP MAX +10 220 440 +10 0.5 UNITS % Hz % V V ns % ms
DS3992
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.
Typical Operating Characteristics
(VCC = 5.0V, TA = +25C, unless otherwise noted.)
ACTIVE SUPPLY CURRENT vs. SUPPLY VOLTAGE
DS3992 toc01
ACTIVE SUPPLY CURRENT vs. TEMPERATURE
9.5 SUPPLY CURRENT (mA) 9.0 8.5 8.0 7.5 7.0 6.5 6.0 GATE QC = 3.5nC fLFOSC = 64kHz DPWM = 100% -40.0 22.5 TEMPERATURE (C) 85.0 VCC = 4.5V VCC = 5.5V VCC = 5.0V
DS3992 toc02
INTERNAL FREQUENCY CHANGE vs. TEMPERATURE
0.8 FREQUENCY CHANGE (%) 0.6 0.4 0.2 0 -0.2 -0.4 -0.6 -0.8 -1.0 -40.0 22.5 TEMPERATURE (C) 85.0 LAMP FREQUENCY DPWM FREQUENCY
DS3992 toc03
9.0 8.5 8.0 SUPPLY CURRENT (mA) 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 GATE QC = 3.5nC fLFOSC = 64kHz SVM 2V DPWM = 10% DPWM = 100% DPWM = 50%
10.0
1.0
4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 SUPPLY VOLTAGE (V)
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Two-Channel, Push-Pull CCFL Controller DS3992
Typical Operating Characteristics (continued)
(VCC = 5.0V, TA = +25C, unless otherwise noted.)
TYPICAL OPERATION AT 16V
DS3992 toc04
BURST DIMMING AT 150Hz AND 10%
DS3992 toc05
TYPICAL STARTUP WITH SVM
2ms 2.0V SVM
DS3992 toc06
10s 5.0V GA 10s 5.0V GB 10s 2.0V LCM 10s 2.0V OVD
1ms 5.0V GA 1ms 5.0V GB 1ms 2.0V LCM
2ms 5.0V GB 2ms 2.0V LCM
1ms 2.0V OVD
2ms 2.0V OVD
BURST DIMMING AT 150Hz AND 50%
DS3992 toc07
SOFT-START AT VINV = 16V
DS3984 toc08
LAMP STRIKE--EXPANDED VIEW
DS3992 toc09
1ms 5.0V GA 1ms 5.0V GB 1ms 2.0V LCM 1ms 2.0V OVD
50s 5.0V GA 50s 5.0V GB 50s 2.0V LCM
1ms 5.0V GA 1ms 5.0V GB 1ms 2.0V LCM 1ms 2.0V OVD
50s 2.0V OVD
LAMP OUT (LAMP OPENED), AUTORETRY DISABLED
DS3992 toc10
0.25 5.0V GA 0.25 5.0V GB LAMP OPENED 0.25 2.00V LCM 0.25 2.00V OVD
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Two-Channel, Push-Pull CCFL Controller
Pin Description
PIN NUMBER 1 NAME LOSC I/O FUNCTION Lamp Oscillator Resistor Adjust. A resistor (RLOSC) to ground on this pin sets the frequency of the lamp oscillator (fLFS:OSC). [RLOSC x fLFS:OSC = 1.6E9]. Burst Dimming DPWM Oscillator Resistor Adjust. A resistor (RPOSC) to ground on this lead sets 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]. Lamp Brightness Control. An analog voltage at this input controls the lamp brightness. See Table 1 for details. Supply Voltage Monitor. The DC inverter supply voltage is monitored by an external resistor divider. 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. MOSFET Gate Drive A for Channel 1. Connect directly to the gate of a logic-level mode n-channel MOSFET. MOSFET Gate Drive B for Channel 1. Connect directly to the gate of a logic-level mode n-channel MOSFET. Lamp Current Monitor Input for Channel 1. Lamp current is monitored by a resistor placed in series with the low-voltage side of the lamp. Over Voltage Detection for Channel 1. Lamp voltage is monitored by a capacitor divider placed on the high-voltage side of the lamp. Signal Ground Supply. 4.5V to 5.5V. MOSFET Gate Drive A for Channel 2. Connect directly to the gate of a logic-level mode n-channel MOSFET. MOSFET Gate Drive B for Channel 2. Connect directly to the gate of a logic-level mode n-channel MOSFET. Lamp Current Monitor Input for Channel 2. Lamp current is monitored by a resistor placed in series with the low-voltage side of the lamp. Overvoltage Detection for Channel 2. Lamp voltage is monitored by a capacitor divider placed on the high-voltage side of the lamp. Supply. 4.5V to 5.5V. Supply. 4.5V to 5.5V.
DS3992
2
POSC
3
BRIGHT
I
4
SVM
I
5 6 7 8 9 10 11 12 13 14 15 16
GA1 GB1 LCM1 OVD1 GND VCC GA2 GB2 LCM2 OVD2 VCC VCC
O O I I O O I I
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Two-Channel, Push-Pull CCFL Controller DS3992
Functional Diagrams
UVLO SYSTEM ENABLE / POR VREF
VCC [4.5V TO 5.5V]
DS3992
2.0V SVM SUPPLY VOLTAGE MONITOR CHANNEL FAULT CHANNEL ENABLE [20.48MHz TO 40.96MHz] x512 PLL TWO INDEPENDENT CCFL CONTROLLERS (SEE FIGURE 2) LCMn LAMP CURRENT MONITOR OVDn OVERVOLTAGE DETECTION
FAULT HANDLING [40kHz TO 80kHz] LOSC EXTERNAL RESISTOR LAMP FREQUENCY SET ANALOG BRIGHTNESS BRIGHT CONTROL POSC EXTERNAL RESISTOR DPWM FREQUENCY SET 90Hz TO 220Hz OR 180Hz TO 440Hz OSCILLATOR (10%) RAMP GENERATOR 40kHz TO 80kHz OSCILLATOR (10%)
GAn MOSFET GBn GATE DRIVERS DPWM SIGNAL
90Hz TO 220Hz OR 180Hz TO 440Hz
GND
Figure 1. DS3992 Functional Diagram
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Two-Channel, Push-Pull CCFL Controller
Functional Diagrams (continued)
LAMP OUT CHANNEL ENABLE CHANNEL FAULT LAMP OVERCURRENT 2.0V DIGITAL CCFL CONTROLLER LAMP STRIKE AND REGULATION 64 LAMP CYCLE INTEGRATOR OVERVOLTAGE 1.0V OVDn OVERVOLTAGE DETECTOR 1.0V GAn MOSFET GATE GBn DRIVERS 400mV LCMn LAMP CURRENT MONITOR
DS3992
DIMMING PWM SIGNAL
512 x LAMP FREQUENCY [20.48MHz TO 40.96MHz]
LAMP MAXIMUM VOLTAGE REGULATION
LAMP FREQUENCY [40kHz TO 80kHz]
GATE DRIVERS
Figure 2. DS3992 Per Channel Logic 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 accurately 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 determine the duty cycle for the MOSFET gates. The DS3992 supports a 1 lamp per channel configuration 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 Circuits section for more information. Block diagrams of the DS3992 are shown in Figures 1 and 2. More operating details of the DS3992 are discussed 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 pulsewidth-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
DPWM SIGNAL
90Hz TO 220Hz OR 180Hz TO 440Hz
LAMP CURRENT
Figure 3. Digital-PWM Dimming and Soft-Start
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Two-Channel, Push-Pull CCFL Controller DS3992
Table 1. BRIGHT Analog Dimming Input Configuration
DEVICE DS3992Z-09P and DS3992Z-18P DS3992Z-09N and DS3992Z-18N SLOPE Positive Negative MINIMUM BRIGHTNESS BRIGHT < 0.5V BRIGHT > 2.0V MAXIMUM BRIGHTNESS BRIGHT > 2.0V BRIGHT < 0.5V
during this time. During the low period of the DPWM cycle, the controller disables the MOSFET gate drivers so the lamp is not driven. This causes the current to stop flowing in the lamp, but the time is short enough to keep the lamp from de-ionizing. Dimming is increased/ decreased by adjusting (i.e., modulating) the burst period duty cycle. At the beginning of each burst dimming cycle, there is a soft-start whereby the lamp current is slowly ramped to reduce the potential to create audible transformer noise. The slope of the BRIGHT dimming input is either positive or negative as shown in Table 1. For voltages between 0.5V and 2.0V, the duty cycle will vary linearly between the minimum and 100%.
The previous formula can now be used to calculate the resistor values for RLOSC and RPOSC as follows: RLOSC = 1600k x kHz = 32k 50kHz 4k x kHz RPOSC = = 25k 0.160kHz
Supply Monitoring
The DS3992 has supply voltage monitors for both the inverter's DC supply (VINV) and its own VCC supply to ensure that both voltage levels are adequate for proper operation. The inverter supply is monitored for undervoltage conditions at the SVM pin. An external resistordivider at the SVM input feeds into a comparator (see Figure 1) having a 2V threshold. Using the equation below to determine the resistor values, the inverter supply trip point (VTRIP) can be customized to shut off the inverter when the inverter supply voltage drops below the specified value. Operating with the inverter voltage at too high of a level can be damaging to the inverter components. Proper use of the SVM can prevent this problem. If desired, SVM can be disabled by connecting the SVM pin to GND. R + R2 VTRIP = 2.0 1 R1 The VCC monitor is a 5V supply undervoltage lockout (UVLO) that prevents operation when the DS3992 does not have adequate voltage for its analog circuitry to operate or to drive the external MOSFETs. The VCC monitor features hysteresis to prevent VCC noise from causing spurious operation when VCC is near the trip point. This monitor cannot be disabled by any means.
Lamp Strike
On lamp strike, the DS3992 boosts the normal operating lamp frequency by 33%. This is done to increase the voltage created and help insure that the lamp strikes. In addition, the maximum strike voltage will be applied to the lamp for over 500ms. Once the controller detects that the lamp has struck, the frequency is returned to the normal lamp frequency.
Setting the Lamp and DPWM Frequencies Using External Resistors Both the lamp and DPWM frequencies are set using external resistors. The resistance required for either frequency can be determined using the following formula:
ROSC = K fOSC
where K = 1600k x kHz for lamp frequency calculations. When calculating the resistor value for the DPWM frequency, K will be one of two values depending on the DS3992 version. If using the -09N/P version (90Hz to 220Hz) then K = 4k x kHz. K = 8k x kHz for the -18N/P version (180Hz to 440Hz). Example: Selecting the resistor values to configure the -09P version to have a 50kHz lamp frequency and a 160Hz DPWM frequency: For the DPWM resistor calculation, K = 4k x kHz. For the lamp-frequency-resistor (RLOSC) calculation, K = 1600k x kHz, which is always the lamp frequency K value regardless of the frequency.
Fault Monitoring
The DS3992 provides extensive fault monitoring for each channel. It can detect open-lamp, lamp overcurrent, failure to strike, and overvoltage conditions. Figure 4 shows a flowchart of how the DS3992 controls and monitors each channel. The steps are as follows: The lamps will not turn on unless the DS3992 supply voltage is > 4.5V and the voltage at the supply voltage monitor (SVM) input is > 2V.
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_____________________________________________________________________
Two-Channel, Push-Pull CCFL Controller DS3992
DEVICE AND INVERTER SUPPLIES AT PROPER LEVELS? YES
FAULT STATE [MUST POWER CYCLE THE DS3992 OR TAKE SVM BELOW 2V TO RESET THE CCFL CONTROLLER]
STRIKE LAMP [RAMP AND REGULATE TO OVD THRESHOLD]
LAMP STRIKE TIMEOUT [65536 LAMP CYCLES]
IF LINE REGULATION THRESHOLD IS MET
OVERVOLTAGE [64 LAMP CYCLES]
LAMP OVERCURRENT [INSTANTANEOUS]
RUN LAMP [REGULATE LAMP CURRENT BOUNDED BY LAMP VOLTAGE]
LAMP-OUT TIMEOUT [65,536 LAMP CYCLES]
MOSFET GATE DRIVERS ENABLED RUN LAMP STAGE
Figure 4. Fault-Handling Flowchart
When both the DS3992 and the DC inverter supplies are at acceptable levels, the DS3992 will attempt to strike the lamps. The DS3992 slowly ramps up the MOSFET gate duty cycle until the lamp strikes. The controller detects that the lamp has struck by detecting current flow in the lamp. If during the strike ramp, the maximum allowable voltage is reached, the controller will stop increasing the MOSFET gate duty cycle to keep from overstressing the system. The DS3992 will go into a fault-handling state if the lamp has not struck after 65,536 lamp cycles. If an overvoltage event is detected during the strike attempt, the DS3992 will disable the MOSFET gate drivers and go into the faulthandling state. Once the lamp is struck, the DS3992 moves to the run lamp stage. In the run lamp stage, the DS3992 adjusts the MOSFET gate duty cycle to optimize the lamp current. The gate duty cycle is always constrained to keep the system from exceeding the maximum allowable lamp voltage. If lamp current ever drops below the lamp out reference point for 65536 lamp cycles, then the lamp is considered extinguished. In this case the MOSFET gate drivers are disabled and the device moves to the fault handling stage.
In the case of a lamp overcurrent condition, the DS3992 will instantaneously declare the controller to be in a fault state. If either channel on the DS3992 goes into the fault state, only the faulty channel will be shut down. Once a fault state is entered, the controller will remain in that state until one of the following occurs: * VCC drops below the UVLO threshold. * The SVM input drops below 2.0V.
Applications Information
Component Selection
External component selection has a large impact on the overall system performance and cost. The two most important external components are the transformers and n-channel MOSFETs. The transformer should be able to operate in the 40kHz to 80kHz frequency range of the DS3992, and the turns ratio should be selected so the MOSFET drivers run at 28% to 35% duty cycle during steady-state operation. The transformer must be able to withstand the high open-circuit voltage that will be used to strike the lamp. Additionally, its primary/secondary resistance and inductance characteristics must be considered because they contribute significantly to determining the
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Two-Channel, Push-Pull CCFL Controller DS3992
efficiency and transient response of the system. Table 2 shows a transformer specification that has been utilized for a 12V inverter supply, 438mm x 2.2mm lamp design. The n-channel MOSFET must have a threshold voltage that is low enough to work with logic-level signals, a low on-resistance to maximize efficiency and limit the nchannel MOSFET's power dissipation, and a breakdown voltage high enough to handle the transient. The breakdown voltage should be a minimum of 3x the inverter voltage supply. Additionally, the total gate charge must be less than QG, which is specified in the Recommended Operating Conditions table. These specifications are easily met by many of the dual nchannel MOSFETs now available in SO-8 packages.
Table 2. Transformer Specifications (as Used in the Typical Operating Circuit )
PARAMETER Turns Ratio (Secondary/Primary) Frequency Output Power Output Current Primary DCR Secondary DCR Primary Leakage Secondary Leakage Primary Inductance Secondary Inductance Secondary Output Voltage 1000ms minimum Continuous 2000 1000 Center tap to one end 5 200 500 12 185 70 500 CONDITIONS (Notes 1, 2, 3) 40 MIN TYP 40 80 6 8 kHz W mA m H mH H mH VRMS MAX UNITS
Note 1: Primary should be Bifilar wound with center tap connection. Note 2: Turns ratio is defined as secondary winding divided by the sum of both primary windings. Note 3: 40:1 is the nominal turns ratio for driving a 438mm x 2.2mm lamp with a 12V supply. Refer to AN3375 for more information.
10
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Two-Channel, Push-Pull CCFL Controller
Typical Operating Circuits
Single Per Channel Operating Circuit
INVERTER SUPPLY VOLTAGE (5V 10% TO 24V 10%) SVM RLCM 1 ILAMP(RMS x 2
DS3992
DUAL POWER MOSFET DEVICE SUPPLY VOLTAGE (5V 10%)
VCC VCC VCC
GA1 RLCM TRANSFORMER GB1 OVERVOLTAGE DETECTION LAMP CURRENT MONITOR
CCFL LAMP
OVD1 LCM1
ANALOG LAMP BRIGHTNESS CONTROL
BRIGHT
DS3992
DUAL POWER MOSFET
GA2 LOSC RESISTOR SET LAMP FREQUENCY TRANSFORMER GB2 OVERVOLTAGE DETECTION LAMP CURRENT MONITOR RLCM
CCFL LAMP
OVD2 POSC RESISTOR SET BURST DIMMING FREQUENCY LCM2 GND
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11
Two-Channel, Push-Pull CCFL Controller DS3992
Typical Operating Circuits (continued)
Multi-Lamp Per Channel Operating Circuit
ON = OPEN OFF/RESET = CLOSED
INVERTER SUPPLY VOLTAGE (12V 10% TO 24V 10%)
SVM
DS3992
1 OF 2 CHANNELS DUAL N-CHANNEL POWER MOSFET DEVICE SUPPLY VOLTAGE (5V 10%)
VCC VCC VCC
GA
CCFL LAMP A
GB
+5V CCFL LAMP B BRIGHT LCM 2N3904
ANALOG LAMP BRIGHTNESS CONTROL
LOSC RESISTOR SET LAMP FREQUENCY +5V CCFL LAMP C 2N3904 POSC RESISTOR SET BURST DIMMING FREQUENCY +5V
2N3904
OVD
GND
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Two-Channel, Push-Pull CCFL Controller
Power-Supply Decoupling
To achieve best results, it is highly recommended that a decoupling capacitor be used on pin 10, the IC powersupply pin. Pins 15 and 16, also VCC pins, do require connection to supply voltage, but do not require any additional decoupling. Typical values of decoupling capacitors are 0.01F or 0.1F. Use a high-quality, ceramic, surface-mount capacitor, and mount it as close as possible to the VCC and GND pins of the IC to minimize lead inductance.
Chip Topology
TRANSISTOR COUNT: 53,000 SUBSTRATE CONNECTED TO GROUND
DS3992
Package Information
For the latest package outline information, go to www.maxim-ic.com/DallasPackInfo.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13
(c) 2006 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
is a registered trademark of Dallas Semiconductor Corporation.
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