LM3432/LM3432B 6-Channel Current Regulator for LED Backlight Application General Description Features The LM3432/LM3432B are 6-channel high voltage current regulators which provide a simple solution for LED backlight applications. These devices incorporate six individual current regulator channels to give accurate driving current for each LED string. The string-to-string tolerance is kept within ±2.0%. Additionally, the Dynamic Headroom Control output can communicate with a LM3430 boost regulator to adjust the LED supply voltage to the lowest level needed to keep the string current in regulation, yielding optimal overall system efficiency. The 6-channel current sink can be adjusted from 15mA to 40mA by an external resistor. Their output drivers can withstand up to 80V. Digital PWM or analog voltage signal can be used to control the duty cycle of all the channels. With a fast current switching slew rate, tr = 60ns typical, accurate current control and wide dimming ratio during PWM dimming are ensured. The LM3432/LM3432B contain LED open/short circuit and over-temperature fault signaling to the system micro-controller (the LM3432B does not include open circuit fault signaling). These devices are available in a low profile, thermally enhanced 24 lead LLP package. The LM3432 is also available in the 28 lead eTSSOP. ■ Dynamic Headroom Control (DHC) output to maximize © 2008 National Semiconductor Corporation 300064 ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ efficiency when used in conjunction with National Semiconductor's LM3430 Boost Controller for LED Backlighting Current sinking adjustable up to 40mA in each string Fast current switching slew rate, tr = 60ns typical Wide dimming ratio, up to 4000:1 with fDIM = 500Hz High LED driving voltage up to 80V ±2.0% current matching between strings Accepts both Digital and Analog dimming control LED open/short fault indication (For LM3432B, no open fault indication) Over-Temperature Indication Internal Thermal Shutdown with Hysteresis Low profile, thermally enhanced LLP-24 (5x4x0.8mm) and eTSSOP-28 (9.7x6.4x1.1mm) packages (The LM3432B is available in the LLP-24 only) Applications ■ LCD display backlight applications ■ General lighting solutions www.national.com LM3432/LM3432B 6-Channel Current Regulator for LED Backlight Application May 22, 2008 LM3432/LM3432B Typical Application Circuit 30006401 www.national.com 2 LM3432/LM3432B Connection Diagrams 30006431 Top View 28 Lead Plastic eTSSOP-28 NS Package Number MXA28A 30006402 Top View 24 Lead Plastic LLP-24 NS Package Number SQA24B Ordering Information Part Number Package Type NS Package Drawing LLP-24 SQA24B Supplied As For LM3432 LM3432SQ LM3432SQX 1000 Units on Tape and Reel LM3432SQE LM3432MH LM3432MHX 4500 Units on Tape and Reel 250 Units on Tape and Reel eTSSOP-28 MXA28A LLP-24 SQA24B Rail of 48 Units 2500 Units on Tape and Reel For LM3432B LM3432BSQ LM3432BSQX 1000 Units on Tape and Reel LM3432BSQE 4500 Units on Tape and Reel 250 Units on Tape and Reel 3 www.national.com LM3432/LM3432B Pin Descriptions Pin Number Name Description LLP-24 eTSSOP-28 1 5 VCC Internal linear regulator output, needs 680nF minimum for stability. 2 6 IREF IOUT current setting pin. An external resistor is used to program the string current. 3 7 AGND Analog ground 4 8 CDHC An external capacitor to ground programs the Dynamic Headroom Control (DHC) response time constant. 5 9 VDHC DHC voltage output. Connecting this output through a gain setting resistor to the DHC pin of National Semiconductor's LM3430 enables the DHC function. 6 10 EN 7 11 MODE 8 12 DIM 9 13 FAULTb 10 14 OTMb 12,13,15,17,19,20 15, 17, 19, 21, 23, 25 IOUT1-6 22 27, 28 PGND 24 1 VIN Supply voltage input, from 6V to 40V. 11,14,16,18,21,23 2, 3, 4, 16, 18, 20, 22, 24, 26 NC No connection and should be left open. EP EP EP Thermal connection pad, connect directly to GND. www.national.com Device Enable, active HIGH. Dimming mode select pin. Short to ground for Digital PWM dimming or connect to an external capacitor to ground for analog dimming. Digital PWM or Analog voltage input for IOUT duty cycle. Open drain active LOW output for output fault. Open drain active LOW over temperature warning output. Constant current sink outputs, adjustable 15mA to 40mA, voltage across this pin can be up to 80V max. Power Ground. 4 If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN Voltage IREF Voltage IOUT1 through IOUT6 Voltage VCC Voltage EN Voltage FAULTb, OTMb Voltage MODE Voltage PWM Voltage VDHC Voltage CDHC Voltage -0.3V to 42V -0.3V to 7V -0.3V to 82V -0.3V to 7V -0.3V to 7V -0.3V to 7V -0.3V to 7V -0.3V to 7V -0.3V to 7V -0.3V to 7V Operating Ranges 2.0kV 215°C 220°C 150°C (Note 1) Supply Voltage, VIN IOUT1 through IOUT6 Voltage Operating Junction Temp. Storage Temperature 6 to 40V 0 to 80V -40°C to +125°C -65°C to +150°C Thermal Resistance, θJA (Note 3) LLP-24 eTSSOP-28 33.2°C/W 29°C/W Electrical Characteristics Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C to +125°C. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. VIN = 18V, RIREF = 54.7 kΩ, VEN = 5V, VMODE = 0V, VDIM = 5V and VOUT1-6 = 1.2V unless otherwise indicated (Note 4). Parameter limits apply to both the LM3432 and LM3432B unless otherwise indicated. Symbol Parameter Conditions Min Typ Max Units 40 90 µA 2.25 2.65 mA 1.75 2 V Input Characteristics ISHDN IQ VEN VEN_HYST IEN Shutdown Input Supply Current EN = 0V, DIM = 0V Quiescent Current from VIN Enable Threshold Voltage VEN rising 1.48 Enable Threshold Hysteresis Enable pin Pull-up Current 0.4 V EN = 0V 0.5 µA EN = 2V 5 VCC Regulator VCCreg VCC Regulated Output 4.7 VCCreg_1 VCC Regulated Output at Max. VIN VIN = 40V VCCreg_2 VCC Regulated Output at Min. VIN VIN = 6V, IVCC = 2mA IVCC_SC VCC Short-Circuit Current VIN = 6V, VCC = 0V VCCUVLO VCC UVLO Upper Threshold VCC rising 4.7 5 5.25 V 5 5.25 V 4.8 V 9 3.9 VCCUVLO_HYST VCC UVLO Hysteresis 4.15 mA 4.4 V 0.375 V Analog PWM control MODE pin Output Current MODE = 2V 34 µA VMODE_PK IMODE MODE pin Peak Voltage CMODE = 5.6nF 3.1 V VMODE_VA MODE pin Valley Voltage CMODE = 5.6nF 1.0 V Digital PWM control VPWM_HIGH PWM Voltage HIGH MODE = GND VPWM_LOW PWM Voltage LOW MODE = GND V 1.7 1 V Dynamic Headroom Control Output VDHC_MAX VDHC pin Max. Output Voltage IVDHC = 2mA 2 2.5 V IVDHC_MAX VDHC pin Max. Output Current VDHC = 1.2V 5 9 mA VDHC_REG_20 VDHC Regulation at 20mA RIREF = 54.7k, CDHC = 100nF 0.625 V VDHC_REG_40 VDHC Regulation at 40mA RIREF = 27.5k, CDHC = 100nF 1.25 V 5 www.national.com LM3432/LM3432B ESD Susceptibility (Note 2) Human Body Model Lead Temperature Vapor Phase (60 sec.) Infra-red (15 sec.) Maximum Junction Temp. Absolute Maximum Ratings (Notes 1, 6) LM3432/LM3432B Symbol Parameter Conditions Min Typ Max Units Switching Characteristics tpd_H Tr IOUT Rising Edge Phase Delay MODE = GND, Pulsing PWM 10µs 500 ns IOUT Rise Time MODE = GND, rising edge from 10% to 90% of IOUT 25 ns Output Current VIREF IREF pin Voltage 6V ≤ VIN ≤ 40V 1.215 1.245 1.27 V IOUT20 Constant Current Sink of 20mA RIREF = 54.7k, VIOUT1-6 = 1.1V 18.85 18.5 20 21.05 21.4 mA IOUT40 Constant Current Sink of 40mA RIREF = 27.5k, VIOUT1-6 = 1.6V 37.9 37.3 40 41.55 42.15 mA IOUT20_match Output Current Matching of IOUT20 (Note 5) 6V ≤ VIN ≤ 40V 2.25 % IOUT40_match Output Current Matching of IOUT40 (Note 5) 6V ≤ VIN ≤ 40V 2 % IOUT_max Maximum Output Current, IREF shorted to GND. VIREF = 0V, VIOUT = 4.5V 80 110 mA 0.3 0.525 V VDROP_IOUT20 Dropout Voltage of IOUT20 (Note 7) RIREF = 54.7k VDROP_IOUT40 Dropout Voltage of IOUT40 (Note 7) RIREF = 27.5k IOUT_OFF Output Current when EN is LOW 50 EN = 0, VOUT = 80V 0.6 1.125 V 0.025 3 µA 7.9 8.8 V Fault Detection VSHORTFAULT VIOUT Short Fault Threshold FAULTb goes LOW during VIOUT rising, other VIOUTs = 1.0V tD_SHORTFAULT Short Fault Delay VIOUT set to 10V, FAULTb goes LOW, other VIOUTs = 1.0V 150 µs tD_OPENFAULT Open Fault Delay (LM3432 only) VIOUTX set open, FAULTb goes LOW 50 µs VFAULT_LOW FAULTb and OTMb LOW 5mA into FAULTb ILEAK_FAULT FAULTb and OTMb Open Leakage VFAULTb = VOTMb = 5V 7.3 0.005 0.7 V 1 µA Thermal Protection OTM Over Temperature Monitor Threshold 125 °C OTMHYST Over Temperature Monitor Hysteresis 20 °C TSD Thermal Shutdown Threshold 165 °C TSDHYST Thermal Shutdown Hysteresis 20 °C Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. The Recommended Operating Limits define the conditions within which the device is intended to be functional. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: The human body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin. Note 3: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ_MAX, the junction-to-ambient thermal resistance, θJA and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using: PD_MAX = (TJ_MAX - TA)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature. Note 4: All limits are guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100% tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. All limits are used to calculate Average Outgoing Quality Level (AOQL). Typical values represent the most likely parametric norm at TJ = 25°C and are provided for reference purposes only. Note 5: IOUT_match is the greatest percentage delta between output string currents with respect to the median. Note 6: Rating limits apply to both the LM3432 and LM3432B. Note 7: Dropout voltage is defined as the IOUT pin to GND voltage at which the output current sink drops 10% from the nominal value. www.national.com 6 Quiescent Current vs Supply Voltage Shutdown Current vs Supply Voltage 30006403 30006404 VCC Regulator Output vs Supply Voltage Current Setting Reference Voltage vs Supply Voltage 30006405 30006406 Average String Current vs Current Setting Resistance Output Current Matching vs Temperature 30006408 30006407 7 www.national.com LM3432/LM3432B Typical Performance Characteristics Unless otherwise specified, the following conditions apply: VIN = 18V, RIREF = 54.7 kΩ, VEN = 5V, VMODE = 0V, VDIM = 5V and VOUT1-6 = 1.2V. Typical performance characteristics are valid for both the LM3432 and LM3432B unless otherwise indicated. LM3432/LM3432B PWM Dimming Frequency vs CMODE PWM Digital Dimming Operation (Channel 1 Waveform) 30006410 30006409 PWM Dimming Characteristic, Rising Edge (Channel 1 Waveform) PWM Dimming Characteristic, Falling Edge (Channel 1 Waveform) 30006411 30006412 Analog Dimming Operation 30006413 www.national.com 8 LM3432/LM3432B Simplified Functional Block Diagram 30006415 9 www.national.com LM3432/LM3432B ANALOG DIMMING OF LED STRINGS Dimming of LED brightness is achieved by Pulse Width Modulation (PWM) control of the string currents. The LM3432/ LM3432B accepts both analog voltage and PWM digital dimming input signals for this feature. With a capacitor (CMODE) connected across the MODE pin and ground, the device will monitor the voltage level at the DIM pin and generate the required PWM control signal internally. The internal implementation of the LM3432/LM3432B’s dimming function is illustrated in Figure 1. Functional Description OVERVIEW The LM3432/LM3432B are 6-channel high voltage current regulators for LED backlight applications which incorporates individual channel current regulators to give accurate current sinking for each LED string. String to string tolerance is kept within ±2.0% at 40 mA and ±2.25% at 20 mA. The 6-channels current sinks can be adjusted from 15 mA to 40 mA by an external resistor. Channel outputs can withstand up to 80V. Channel 5 or 6 output can be disabled by shorting the selected output pin to ground prior to power-up. Both the digital PWM dimming signal and analog voltage signal can be used to control the duty cycle of all the six channels. The LM3432/ LM3432B also provide fault indications to the system MCU for an LED open (included in the LM3432 only) or short circuit or an over-temperature condition. INTERNAL 5V LINEAR REGULATOR An internal 5V linear regulator with an Under-Voltage LockOut (UVLO) function is integrated within the LM3432/ LM3432B. This regulated 5V is used for internal circuitry and can support a small amount of external loading, not to exceed 2 mA when VIN = 6V. The supply input pin (VIN) can be connected directly to an input voltage up to 40V, with transient capability up to 42V. The VCC output regulates at 5V and is current limited to 9 mA. To ensure stable operation, the external capacitor CVCC must be at least 680 nF with 1 µF recommended. If the voltage at the VCC pin drops below the UVLO threshold of 3.8V, the device will shut down the output channels and other functional blocks. Normal operation will be resumed once the VCC voltage is allowed to rise above the UVLO rising threshold of 4.15V. 30006417 FIGURE 1. Analog Dimming of LEDs An internal current source of 34 µA (typical) will charge the external capacitor (CMODE) linearly until it reaches 3V. The comparator (Comp1) then forces CMODE to be discharged to 1V very quickly. By repeating the cycle, a saw-tooth waveform as shown in Figure 1 is generated. Comparator (Comp2) compares this ramp waveform with the external dc voltage at the DIM pin generating the desired PWM control signal. When VDIM ≤ 1V, ON duty factor, DON = 0% and when VDIM ≥ 3V, DON = 100%. The frequency of the PWM control signal can be calculated as shown below. BANDGAP VOLTAGE REFERENCE A precision reference voltage is required for accurate control of the output currents. The LM3432/LM3432B contain a bandgap voltage reference block that provides a high precision reference voltage for internal operation. The bandgap reference voltage is typically trimmed to 1.245V. OUTPUT CURRENT REGULATOR (IOUT1 to IOUT6) The LM3432/LM3432B contains six individual integrated current regulators to give accurate current sinking for each LED string. String to string tolerance is kept within ±2.0% at 40 mA and ±2.25% at 20 mA. The sink current level is adjusted by an external resistor, RIREF in the range of 15 mA to 40 mA. The IOUT pins can withstand up to 80V. The ability to withstand high voltage enables the user to add more LEDs in a single string. The calculation of IOUT with respect to RIREF is shown below. Or PWM DIGITAL DIMMING of LED STRINGS Alternatively, the dimming control can be implemented by direct application of a digital signal to the device. With the MODE pin connected to ground, an externally applied PWM dimming signal is applied to the DIM pin. The peak amplitude of the externally applied PWM signal should be greater than 1.5V to guarantee clean PWM switching. During PWM dimming, channels are not switched simultaneously in an effort to minimize large surge currents from being drawn from the LED supply rail. Each channel will have 0.5 µs phase delay with respect to the preceding channel. As a consequence of the phase delay, for a control pulse width less Channels 5 and 6 are designed to be user disabled without activating the fault detection circuitry. With this feature, the user can readily configure the device to a 4, 5 or 6 channel driver. In order to disable a channel, the IOUT5 and/or IOUT6 pin(s) must be tied to ground before powering up the device. During power-up, channels 5 and 6 will be checked and any grounded channel(s) will be automatically disabled. The disabled status will remain until either power is recycled or the enable (EN) pin is toggled. www.national.com 10 the finest pulse width resolution that can be realized. The PWM switching timing for all six channels is shown in Figure 2. 30006420 FIGURE 2. PWM Dimming Switching Timing detect feature will be active for all channels. In the event an LED short fault condition occurs and causes the voltage between any of the IOUT pin and ground to exceed the typical short fault threshold of 7.9V for more than 150 μs, the affected channel(s) will be latched off and the FAULTb pin will be pulled to ground. The affected channel(s) will remain latched off until recycling power or toggling the EN pin. All of the other channels that are not affected will continue to function normally. If the voltages between all IOUT pins and ground are greater than 2V typical, the Short Fault Detect feature will be disabled to prevent false triggering of the short fault detect function. LED SHORT FAULT DETECT With DHC If the Dynamic Headroom Control (DHC) feature is used, the lowest voltage between the IOUT pins and ground among the strings will be regulated to 0.625V typical (ILED = 20 mA) by lowering the LED supply rail voltage, VLED. If an LED short fault condition occurs and causes the voltage between any of the IOUT pins and ground to exceed the typical short fault threshold of 7.9V for more than 150 µs, the affected channel (s) will be latched off and the FAULTb pin will be pulled to ground. The affected channel(s) will remain latched off until recycling power or toggling the EN pin. All of the other channels that are not affected will continue to function normally. LED OPEN FAULT DETECT (LM3432 ONLY) For the LM3432, if an open fault should occur and the affected channel sinks no current for greater than 50 µs, it will be latched off (until recycling power or toggling EN pin). The FAULTb pin’s output will be pulled to ground while the other channels keep functioning normally. The open fault detection and FAULTb indication features are inactive in the LM3432B. Without DHC In applications where the DHC function is not used, the IOUT pin voltage on each string will be the voltage difference between the LED supply rail voltage, VLED, and the voltage drop across the entire LED string. If the voltage between any of the IOUT pins and ground is less than 2V typical, the short fault 11 www.national.com LM3432/LM3432B than 0.5 µs, the duty cycle will be rounded down to 0% and for a control pulse width less than 0.5 µs off time, the duty cycle will be rounded up to 100%. Therefore, 0.5µs becomes LM3432/LM3432B 30006429 FIGURE 3. Fault Detect Functional Block Diagram OVER-TEMPERATURE MONITOR If the LM3432/LM3432B junction temperature exceeds approximately 125°C, the OTMb pin will be pulled to ground but the part will continue to function. Action must be taken to lower the temperature at this point. The PWM duty factor may be lowered as an example to reduce the amount of heat generated, which will in turn lower the die temperature. If the junction temperature is allowed to rise beyond approximately 165°C, the part will shut down. When the device is cooled down to about 145°C, device operation will resume. Note that this thermal shutdown protection is only intended as a fault mode protection feature. Device operation above rated maximum operating junction temperature is neither recommended nor guaranteed. www.national.com DYNAMIC HEADROOM CONTROL To use the DHC function, connect a gain setting resistor from the VDHC pin of the LM3432/LM3432B to the VDHC pin of the LM3430 (National Semiconductor’s Boost Controller for LED Backlighting) that is supplying power to the LED rails. The LM3432/LM3432B’s DHC function will regulate the voltage between the IOUT pins and ground to a minimum of 0.625V typical (IOUT = 20 mA) to optimize overall efficiency. A large DHC time constant needs to be set in order not to interfere with the loop response of the DC-DC converter. This can be implemented by connecting a capacitor from the LM3432/LM3432B’s CDHC pin to ground. If the DHC function is not needed, leave the VDHC pin floating. When operated in this manner, if the lowest voltage between any of the IOUT pins and ground is greater than 2V, the LED short fault detection function will be disabled. For the LM3432B, if any open condition occurs on any channels, the DHC function will be inactive and the LED supply rail voltage from the LM3430 will stay at its preset level. If the excess headroom voltage is greater than the short fault detect threshold, 7.3V(min), the device may latch off the LED string(s) due to short fault protection. In order to insure the proper operation of good LED strings, designers must design for sufficient excess headroom voltage below the short fault detect threshold. 12 The LM3432/LM3432B provide a simple and handy solution for LED driving. With only a few external passive components, 30006421 FIGURE 4. Typical Application Schematic to Drive 72 White LEDs (@20 mA) (PWM Digital Dimming) For the example shown in Figure 4, the string current is 20 mA. Applying to the equation: DETERMINATION OF EXTERNAL COMPONENTS The typical application only requires three external components. The selection of those components is described in detail below. Programming of String Current, IOUT1 to IOUT6 The string current can be programmed by an external resistor, RIREF. The equation to calculate the resistance of this resistor is shown below. Selecting the VCC Output Capacitor, CVCC For proper operation, a VCC output capacitor (CVCC) of at least 680 nF is required for stability reason. The recommended CVCC capacitance is 1 µF. In order to ensure good current regulation over the full operating temperature range, a high quality resistor with ±1% tolerance and a low temperature coefficient is recommended. 13 www.national.com LM3432/LM3432B an LED panel of up to about 120 white LEDs can be illuminated. A typical application configuration driving six strings with twelve white LEDs per string is shown in Figure 4. Applications Information LM3432/LM3432B Driving High Current LEDs The LM3432/LM3432B can support string currents from 15 mA to 40 mA. If the application needs to drive high current LEDs that require more than 40 mA per string, the LM3432/ LM3432B provides the alternative of connecting several IOUT ports together to achieve higher output current per string. With this approach, there is the obvious trade off between higher output current and number of strings driven. Two possible configurations are illustrated in Figure 5. Selecting the VIN Capacitor, CVIN The purpose of this capacitor is to supply transient current to the device and suppress VIN noise in order to ensure proper operation. A low ESR ceramic capacitor with good high frequency performance is recommended. The capacitance can range from 0.1 µF to 1 µF. Analog Dimming Control If analog dimming control is required, a capacitor, CMODE should be connected from the MODE pin to ground instead of shorting the MODE pin to ground. The relationship between the PWM dimming frequency and the capacitance of CMODE is illustrated below. When VPWM ≤ 1V, DON = 0% and when VPWM ≥ 3V, DON = 100% The LED dimming ratio is calculated from the ratio of minimum ON duty factor to the maximum ON duty factor. With the LM3432/LM3432B, the LEDs can be fully turned on up to 100% ON duty factor and the minimum ON duty factor is limited by the phase delay time, 0.5 µs. The dimming ratio can be estimated as below. As an example, if the PWM dimming frequency is set to 500 Hz, the best achievable dimming ratio is: www.national.com 14 LM3432/LM3432B 30006427 FIGURE 5. Achieving Higher LED String Current by Grouping IOUT Ports must be set to a large enough value by adding a capacitor from CDHC pin to ground. Figure 6 is an application schematic of a LED panel driver using both the LM3430 and the LM3432/LM3432B with the Dynamic Headroom Control function enabled. The LM3430 boosts a voltage from VIN to 50V nominal to supply the LED strings. With the DHC function disabled, the LM3430 will keep the LED string supply regulated at 50V. When the DHC is enabled, this voltage will dynamically be regulated down to a voltage that can just keep all LED string currents in regulation. That is about 40V in the application shown in Figure 6. The reduction in this rail voltage can significantly improve the overall system efficiency. Dynamic Headroom Control, DHC with LM3430 When the LM3432/LM3432B are powered with National Semiconductor's Boost Controller for LED Backlighting, LM3430, the Dynamic Headroom Control (DHC) feature helps to provide the optimal system efficiency. By connecting VDHC through a gain setting resistor to the DHC pin of the LM3430 that is supplying the LED power rail, the LM3432/ LM3432B’s DHC function will regulate the minimum of the ON voltage of the six channels to 0.625V typical (IOUT = 20 mA). This is the minimum voltage headroom required at outputs to keep the current regulator in its linear operating range. In order not to interfere with the feedback loop response of the upstream DC-DC converter, the DHC response time constant 15 www.national.com LM3432/LM3432B 30006428 FIGURE 6. LM3430 + LM3432/LM3432B Application Schematic with Dynamic Headroom Control Enabled www.national.com 16 LM3432/LM3432B Physical Dimensions inches (millimeters) unless otherwise noted 24-Lead LLP Package NS Package Number SQA24B 28-Lead eTSSOP Package NS Package Number MXA28A 17 www.national.com LM3432/LM3432B 6-Channel Current Regulator for LED Backlight Application Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH www.national.com/webench Audio www.national.com/audio Analog University www.national.com/AU Clock Conditioners www.national.com/timing App Notes www.national.com/appnotes Data Converters www.national.com/adc Distributors www.national.com/contacts Displays www.national.com/displays Green Compliance www.national.com/quality/green Ethernet www.national.com/ethernet Packaging www.national.com/packaging Interface www.national.com/interface Quality and Reliability www.national.com/quality LVDS www.national.com/lvds Reference Designs www.national.com/refdesigns Power Management www.national.com/power Feedback www.national.com/feedback Switching Regulators www.national.com/switchers LDOs www.national.com/ldo LED Lighting www.national.com/led PowerWise www.national.com/powerwise Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors Wireless (PLL/VCO) www.national.com/wireless THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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