LT3479 3A, Full Featured DC/DC Converter with Soft-Start and Inrush Current Protection FEATURES DESCRIPTION n The LT®3479 is a current mode, fixed frequency step-up DC/DC converter with an internal 3A, 42V switch. Efficiencies of up to 89% can be achieved in typical applications. It features a programmable soft-start function to limit inductor current during start-up and inrush current protection to protect the LT3479 during shorts and line transients. Both inputs of the error amplifier are available to the user allowing positive and negative output voltages. Through an external resistor, the user can program the switching frequency from 200kHz to 3.5MHz. The low profile (0.75mm) 14-pin, 4mm × 3mm DFN package provides excellent thermal performance in a small footprint. The LT3479 is also available in a thermally enhanced 16-pin TSSOP package. n n n n n n n n Wide Input Voltage Range: 2.5V to 24V 3A, 42V Internal Switch High Efficiency Power Conversion: Up to 89% Soft-Start Frequency Set by External Resistor: 200kHz to 3.5MHz Protection Against Input Short Circuits and Hot Plugging Low VCESAT Switch: 0.3V at 2.5A (Typical) Capable of Positive and Negative Outputs Available in Thermally Enhanced 14-Lead (4mm × 3mm) DFN and 16-Lead TSSOP Packages APPLICATIONS n n n L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. High Power LED Driver DSL Modems Distributed Power TYPICAL APPLICATION 5V to 12V Boost Converter 5V to 12V Efficiency 4.7μH 200k SW FBN SHDN 23.2k LT3479 VREF GND FBP VC SS 10nF RT 85 10μF EFFICIENCY (%) 2.2μF VIN VS L 90 VOUT 12V 0.8A VIN 5V 80 75 70 65 10k 17.8k 2.2nF 3479 TA01 60 0 0.2 0.4 0.6 0.8 IOUT (A) 3479 TA02 3479fb 1 LT3479 ABSOLUTE MAXIMUM RATINGS (Note 1) SW, L, VS Voltages ................................................... 42V VIN, SHDN Voltages ................................................. 24V FBP, FBN, VREF, RT, VC Voltages ................................. 2V Junction Temperature .......................................... 125°C Operating Temperature Range (Note 2).... –40°C to 85°C Storage Temperature Range................... –65°C to 125°C Lead Temperature (Soldering, 10 sec) TSSOP .............................................................. 300°C PIN CONFIGURATION TOP VIEW TOP VIEW SW 1 16 GND SW 1 14 GND SW 2 15 GND SW 2 13 GND L 3 14 GND L 3 12 SS VS 4 VS 4 VIN 5 10 FBN VIN 5 RT 6 9 FBP RT 6 11 FBN SHDN 7 8 VREF SHDN 7 10 FBP GND 8 9 15 11 VC DE14 PACKAGE 14-LEAD (4mm s 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 43°C/W EXPOSED PAD (PIN 15) IS PGND (MUST BE SOLDERED TO PCB) 17 13 SS 12 VC VREF FE PACKAGE 16-LEAD PLASTIC TSSOP TJMAX = 125°C, θJA = 38°C/W EXPOSED PAD (PIN 17) IS PGND (MUST BE SOLDERED TO PCB) ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3479EDE#PBF LT3479EDE#TRPBF 3479 14-Lead (4mm × 3mm) Plastic DFN –40°C to 85°C LT3479EFE#PBF LTC4263IDE#TRPBF 3479EFE 16-Lead Plastic TSSOP –40°C to 85°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3479EDE LT3479EDE#TR 3479 14-Lead (4mm × 3mm) Plastic DFN –40°C to 85°C LT3479EFE LT3479EFE#TR 3479EFE 16-Lead Plastic TSSOP –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 3479fb 2 LT3479 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 2.5V, VSHDN = 2.5V. PARAMETER CONDITIONS MIN l Minimum Input Voltage Quiescent Current VIN = 2.5V, VSHDN = 0V VIN = 2.5V, VSHDN = 2.5V, VC = 0.3V (Not Switching) Reference Voltage Measured at VREF Pin Reference Voltage Line Regulation 2.5V < VIN < 24V, VC = 0.3V Maximum VREF Pin Current Out of Pin Soft-Start Pin Current SS = 0.5V, Out of Pin l 1.216 TYP MAX 2.3 2.5 V 0.1 5 1 7.5 μA mA 1.235 1.250 V 0.01 0.03 %/V 100 μA 9 UNITS μA FBP Pin Bias Current 25 100 nA FBN Pin Bias Current 25 100 nA 2 6 mV Feedback Amplifier Offset Voltage FBP – FBN, VC = 1V –2 Feedback Amplifier Voltage Gain 250 V/V Feedback Amplifier Transconductance 150 μS Feedback Amplifier Sink Current VFBP = 1.25V, VFBN = 1.5V, VC = 0.5V 10 μA Feedback Amplifier Source Current VFBP = 1.25V, VFBN = 1V, VC = 0.5V 10 μA Switching Frequency RT = 17.8k RT = 113k RT = 1.78k Maximum Switch Duty Cycle RT = 17.8k SHDN Pin Current VSHDN = 5V VSHDN = 0V SHDN Pin Threshold l 0.9 160 2.7 1 200 3.5 84 93 0.3 1.15 240 4.1 MHz kHz MHz % 30 0.1 60 1 μA μA 1.5 2 V Inductor Current Limit (Note 3) 3.5 5 6.5 A Switch Current Limit (Note 3) 3 4.5 6 A Switch VCESAT ISW = 1A (Note 3) 120 200 mV Switch Leakage Current SW = 40V 0.2 5 μA Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT3479 is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. Note 3: Inductor Current Limit, Switch Current Limit and Switch VCESAT for DE package guaranteed by design and/or correlation to static test. 3479fb 3 LT3479 TYPICAL PERFORMANCE CHARACTERISTICS Switch VCE(SAT) Inductor and Switch Current Limit VREF 6 0.5 1.27 INDUCTOR CURRENT LIMIT 0.3 25°C –50°C 0.2 0.1 0.5 1 1.5 2 SWITCH CURRENT (A) 2.5 3 1.25 SWITCH CURRENT LIMIT 3 VIN = 24V 1.24 VIN = 2.5V 2 1.23 1 1.22 0 –50 –25 0 0 4 VREF (V) CURRENT (A) 125°C VCE(SAT) (V) 1.26 5 0.4 50 25 75 0 TEMPERATURE (°C) 100 1.21 –50 –25 125 SHDN Pin Turn-On Threshold 3479 G03 SHDN Pin Current VIN Pin Current 50 1.750 6 SHDN THRESHOLD (V) 1.375 30 25°C 20 125°C 10 0 75 0 25 50 TEMPERATURE (°C) –25 100 125 0 8 4 12 20 Soft-Start Pin Current 3 2 –50 –25 24 Oscillator Frequency Feedback Amplifier Offset Voltage RT = 10k FREQUENCY (MHz) 1.2 RT = 15k 0.8 RT = 20k 4 5 0.4 25 50 75 100 125 150 TEMPERATURE (°C) 3479 G07 25 50 75 100 125 150 TEMPERATURE (°C) 5 1.6 15 10 0 3479 G06 2.0 0 4 3479 G05 20 0 –50 –25 5 VSHDN (V) 3479 G04 ISS (μA) 16 OFFSET VOLTAGE (mV) 1.250 –50 VC = 0.3V 40 VIN PIN CURRENT (mA) SHDN PIN CURRENT (μA) –50°C 1.500 25 50 75 100 125 150 TEMPERATURE (°C) 3479 G02 3479 G01 1.625 0 0 –50 –25 VC = 0.5V 3 VC = 1V 2 1 0 25 50 75 100 125 150 TEMPERATURE (°C) 3479 G08 0 –50 –25 0 25 50 TEMPERATURE (oC) 75 100 3479 G09 3479fb 4 LT3479 PIN FUNCTIONS (DFN/TSSOP) SW (Pins 1, 2/Pins 1, 2): Switch Pins. Collector of the internal NPN power switch. Connect the inductor and diode here and minimize the metal trace area connected to this pin to minimize electromagnetic interference. FBP (Pin 9/Pin 10): The Noninverting Input to the Error Amplifier. Connect resistive divider tap here for negative output voltage. L (Pin 3/Pin 3): Inductor Pin. Connect the inductor to this pin. FBN (Pin 10/Pin 11): The Inverting Input to the Error Amplifier. Connect resistive divider tap here for positive output voltage. VS (Pin 4/Pin 4): Inductor Supply. Must be locally bypassed. Powers the switch and the inductor. In case only one supply voltage is available, tie VIN and VS together. VC (Pin 11/Pin 12): Compensation Pin for Error Amplifier. Connect a series RC from this pin to GND. Typical values are 10kΩ and 2.2nF. VIN (Pin 5/Pin 5): Input Supply. Must be locally bypassed. Powers the internal control circuitry. SS (Pin 12/Pin 13): Soft-Start. Place a soft-start capacitor here. Leave floating if not in use. RT (Pin 6/Pin 6): Timing Resistor Pin. Adjusts the switching frequency. Do not leave this pin open. See Table 4 for RT values and switching frequencies. GND (Pins 13, 14/Pins 8, 14, 15, 16): Ground. Tie directly to local ground plane. SHDN (Pin 7/Pin 7): Shutdown. Tie to 1.5V or greater to enable the device. Tie below 0.3V to turn off the device. Exposed Pad (Pin 15/Pin 17): Power Ground. Must be connected to electrical PCB ground. VREF (Pin 8/Pin 9): Bandgap Voltage Reference. Internally set to 1.235V. Connect this pin to FBP if generating a positive output, or to an external resistor divider if generating a negative voltage. This pin can provide up to 100μA of current and can be locally bypassed with a 100pF capacitor. 3479fb 5 LT3479 BLOCK DIAGRAM D1 L1 RC CC CSS CS C1 R1 FB VS SS FBP + FEEDBACK AMPLIFIER R2 8.5mW INRUSH CURRENT PROTECTION COMPARATOR + FBN SW L + – 36mV VC – – VREF SHDN ICON MASTER LATCH + pwmout 1.25V REFERENCE SLOPE VIN CIN – PWM COMPARATOR R DRIVER t RT Q1 Q S + 3 OSCILLATOR RT t CURRENT LIMIT COMPARATOR – GND 3479 BD 3479fb 6 LT3479 OPERATION The LT3479 uses a fixed frequency, current mode control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the Block Diagram. The start of each oscillator cycle sets the SR latch and turns on power switch Q1. The signal at the inverting input of the PWM comparator (SLOPE) is proportional to the sum of the switch current and oscillator ramp. When SLOPE exceeds VC (the output of the feedback amplifier), the PWM comparator resets the latch and turns off the power switch. In this manner, the feedback amplifier and PWM comparators set the correct peak current level to keep the output in regulation. The LT3479 also features a soft-start function. During start-up, 10μA of current charges the external soft-start capacitor. The SS pin directly limits the rate of voltage rise on the VC pin, which in turn limits the peak switch current. The switch current is constantly monitored and not allowed to exceed the nominal value of 3A. If the switch current reaches 3A, the SR latch is reset regardless of the output of the PWM comparator. Current limit protects the power switch and external components. Soft-start plays an important role in applications where the switch will reach levels of 30V or higher. During startup, an overshoot in the switch current together with the presence of high switch voltage can overstress the switch. A properly used soft-start feature will greatly improve the robustness of such designs. In addition to soft-start, inrush current protection protects the LT3479 against shorts and line transients. During such faults, the inductor current can momentarily exceed 3A and damage the switch. Through an internal 8.5mΩ resistor placed in series with the inductor, the inrush current protection comparator measures the inductor current. If it exceeds 5A, a soft-start cycle is initiated. The LT3479 will remain in the soft-start condition until the fault has passed. 3479fb 7 LT3479 APPLICATIONS INFORMATION Capacitor Selection Low ESR (equivalent series resistance) ceramic capacitors should be used at the output to minimize the output ripple voltage. Use only X5R or X7R dielectrics, as these materials retain their capacitance over wider voltage and temperature ranges better than other dielectrics. A 4.7μF to 10μF output capacitor is sufficient for most high output current designs. Converters with lower output currents may need only a 1μF or 2.2μF output capacitor. Table 1. Ceramic Capacitor Manufacturers MANUFACTURER PHONE WEB Taiyo Yuden (408) 573-4150 www.t-yuden.com AVX (803) 448-9411 www.avxcorp.com Murata (714) 852-2001 www.murata.com Inductor Selection can pass a current larger than its rated value without damaging it. Aggressive designs where board space is precious will exceed the maximum current rating of the inductor to save board space. Consult each manufacturer to determine how the maximum inductor current is measured and how much more current the inductor can reliably conduct. Physically larger inductors provide better efficiency than smaller ones. Figure 1 shows a 3% to 4% efficiency gain in using a larger inductor in a 1MHz, 5V to 12V application. The efficiency of the TOKO FDV0630-4R7M, which measures 7mm × 7.7mm and 3 mm thick, peaks at 87%. The smaller Sumida CDRH4D28-4R7 which is 5mm × 5mm and 3mm thick yields a peak efficiency of 85% in an identical application. Thus, if board space is abundant, then larger inductors should be used to maximize efficiency. 90 Several inductors that work well with the LT3479 are listed in Table 2. However, there are many other manufacturers and devices that can be used. Consult each manufacturer for more detailed information and their entire range of parts. Ferrite core inductors should be used to obtain the best efficiency. Choose an inductor that can handle the necessary peak current without saturating, and ensure that the inductor has a low DCR (copper-wire resistance) to minimize I2R power losses. A 4.7μH or 10μH inductor will suffice for most LT3479 applications. 85 EFFICIENCY (%) 80 TOKO FDV0630-4R7 75 SUMIDA CDRH4D28-4R7 70 65 60 55 50 0 0.2 0.4 0.6 0.8 IOUT (A) Inductor manufacturers specify the maximum current rating as the current where the inductance falls to some percentage of its nominal value—typically 65%. An inductor 3479 F01 Figure 1. Efficiency vs Inductor Size Table 2. Suggested Inductors MANUFACTURER PART NUMBER IDC (A) INDUCTANCE (μH) MAX DCR (mΩ) L×W×H (mm) CDRH6D283R0 CDRH6D28100 CDRH4D284R7 3 1.7 1.32 3 10 4.7 24 65 72 6.7 × 6.7 × 3.0 6.7 × 6.7 × 3.0 5.0 × 5.0 × 3.0 Sumida www.sumida.com LM N 05D B4R7M LM N 05D B100K 2.2 1.6 4.7 10 49 10 5.9 × 6.1 × 2.8 5.9 × 6.1 × 2.8 Taiyo Yuden www.t-yuden.com LQH55DN4R7M01L LQH55DN100M01K 2.7 1.7 4.7 10 57 130 5.7 × 5.0 × 4.7 5.7 × 5.0 × 4.7 Murata www.murata.com FDV0630-4R7M 4.2 4.7 49 7.0 × 7.7 × 3.0 Toko www.toko.com MANUFACTURER 3479fb 8 LT3479 APPLICATIONS INFORMATION Diode Selection Setting Negative Output Voltages Schottky diodes, with their low forward voltage drop and fast switching speed, are ideal for LT3479 applications. Table 3 lists several Schottky diodes that work well with the LT3479. The diode’s average current rating must exceed the average output current. The diode’s maximum reverse voltage must exceed the output voltage. The diode conducts current only when the power switch is turned off (typically less than 50% duty cycle), so a 3A diode is sufficient for most designs. The companies below also offer Schottky diodes with high voltage and current ratings. To set a negative output voltage, select the values of R3 and R4 (see Figure 3) according to the following equation: ⎛ R3 ⎞ VOUT = –1.235V⎜ ⎟ ⎝ R4 ⎠ –VOUT R3 FBP R4 LT3479 VREF Table 3. Suggested Diodes FBN MANUFACTURER MAX MAX REVERSE PART NUMBER CURRENT (A) VOLTAGE (V) MANUFACTURER UPS340 UPS315 3 3 40 15 Microsemi www.microsemi.com B220 B230 B240 B320 B330 B340 SBM340 2 2 2 3 3 3 3 20 30 40 20 30 40 40 Diodes, Inc www.diodes.com Setting Positive Output Voltages To set a positive output voltage, select the values of R1 and R2 (see Figure 2) according to the following equation: ⎛ R1⎞ VOUT = 1.235V⎜ 1 + ⎟ ⎝ R2 ⎠ 3479 F03 Figure 3. Negative Output Voltage Feedback Connections Board Layout As with all switching regulators, careful attention must be paid to the PCB board layout and component placement. To maximize efficiency, switch rise and fall times are made as short as possible. To prevent radiation and high frequency resonance problems, proper layout of the high frequency switching path is essential. Minimize the length and area of all traces connected to the SW pin and always use a ground plane under the switching regulator to minimize interplane coupling. The signal path including the switch, output diode D1 and output capacitor COUT, contains nanosecond rise and fall times and should be kept as short as possible. Recommended component placement is shown in Figure 4. FBP LT3479 VOUT VREF R1 FBN R2 3479 F02 Figure 2. Positive Output Voltage Feedback Connections Soft-Start For many applications, it is necessary to minimize the inrush current at start-up. The built-in soft-start circuit significantly reduces the start-up current spike and output voltage overshoot. A typical value is 10nF for 1.65ms. Figure 5 shows the start-up output voltage and inductor current waveforms in a typical application without a soft-start capacitor. Notice the output voltage overshoot and the large initial current. The addition of a 22nF capacitor eliminates the output overshoot and reduces the peak inductor current (Figure 6). 3479fb 9 LT3479 APPLICATIONS INFORMATION MINIMIZE THE AREA OF THIS TRACE TO VOUT D COUT L1 CC TO VS SW GND SW GND CS CIN RT RC SS L VC LT3479 VS TO VIN CSS VIN FBN RT FBP R1 VREF SHDN R2 TO GND 3479 F04 TO SHDN PLACE VIAS AROUND EXPOSED PAD TO ENHANCE THERMAL PERFORMANCE Figure 4. Suggested Board Layout Switching Frequency IL 2A/DIV The switching frequency of the LT3479 is set by an external resistor attached to the RT pin. Do not leave this pin open. A resistor must always be connected for proper operation. See Table 4 and Figure 7 for resistor values and corresponding frequencies. VOUT 5V/DIV 0.2MS/DIV 3479 F05 Figure 5. Start-Up with No Soft-Start Capacitor IL 2A/DIV VOUT 5V/DIV 0.2ms/DIV SWITCHING FREQUENCY (MHz) RT (kΩ) 3.5 1.78 3 2.87 2.5 4.32 2 6.49 1.5 10.2 1 17.8 0.5 39.2 0.2 113 3479 F06 Figure 6. Start-Up with CSS = 22nF 10 Table 4. Switching Frequency 3479fb LT3479 APPLICATIONS INFORMATION Increasing switching frequency reduces output voltage ripple but also reduces efficiency. The user should set the frequency for the maximum tolerable output voltage ripple. Figure 8 shows a reduction in efficiency of about 4% between 1MHz and 2MHz operation in a typical application. Inrush Current Protection The LT3479 features a novel inductor current sensing circuit that protects the LT3479 during hot plugging and short circuits. An internal resistor in series with the external inductor senses the inductor current at all times. When it exceeds 5A, a soft-start cycle is initiated. Figure 9 shows an output overload with inrush current protection disabled. Notice that soft-start remains high, and that the inductor current does not return to zero. Figure 10 illustrates the benefits of inrush current protection. The output short initiates a new soft start cycle reducing the inductor current. After the fault has passed, the inductor current slowly returns to its equilibrium value. To ensure bond wire integrity, the inductor current should not exceed 8A for more than 10ms. Bypassing the 8.5mΩ inductor current sense resistor disables inrush current protection. Connect the inductor supply trace and bypass capacitor to the L pin and leave the VS pin open to disable this feature. 3.5 VSW 10V/DIV SWITCH FREQUENCY (MHz) 3.0 2.5 IL 4V/DIV 2.0 VSS 2V/DIV 1.5 VOUT 20V/DIV 1.0 3479 F09 20μs/DIV 0.5 0 0.1 Figure 9. Output Overload with Inrush Current Protection Enabled 100 10 RT (kΩ) 3479 F07 Figure 7. Switching Frequency VSW 10V/DIV IL 4V/DIV 90 1MHz 85 80 EFFICIENCY (%) VSS 2V/DIV 2MHz VOUT 20V/DIV 75 3479 F10 70 20μs/DIV 65 Figure 10. Output Overload with Inrush Current Protection Disabled 60 55 VIN 50 0 0.2 0.4 0.6 0.8 IOUT (A) VOUT LT3479 BOOST REGULATOR 0.5Ω 3479 F08 Figure 8. Efficiency vs Switching Frequency 3479 F11 Figure 11. Circuit for Output Overload 3479fb 11 LT3479 TYPICAL APPLICATIONS 5V to 12V/800mA 1MHz Boost Converter 90 D1 C1 2.2μF 200k VIN VS L SW FBN SHDN C2 10μF VOUT 12V 0.8A 80 23.2k LT3479 VREF SS RT GND 85 EFFICIENCY (%) VIN 5V L1 4.7μH Efficiency FBP VC 75 70 65 60 55 10nF 10k 17.8k 50 2.2nF 0 0.2 0.4 0.6 C1: TAIYO YUDEN LMK316BJ225MD C2: AVX 1206 YD106MAT D1: DIODES INC B320A L1: TOKO FDV0630-4R7M 3479 TA03b 5V to 12V/800mA 500kHz Boost Converter L1 10μH C1 2.2μF 90 D1 200k VIN VS L SW FBN SHDN 23.2k LT3479 VREF SS RT GND Efficiency FBP VC C2 10μF VOUT 12V 0.8A 85 80 EFFICIENCY (%) VIN 5V 0.8 IOUT (A) 3479 TA03 75 70 65 60 55 10nF 39.2k 4.7k 50 10nF 3479 TA04 C1: TAIYO YUDEN LMK316BJ225MD C2: AVX 1206 YD106MAT D1: DIODES INC. B320A L1: SUMIDA CDRH8D43-100 0 0.2 0.4 0.6 0.8 IOUT (A) 3479 TA04b 3479fb 12 LT3479 TYPICAL APPLICATIONS 3.3V to 8V/900mA Boost Converter 90 D1 C1 2.2μF C2 10μF 169k VIN VS L SW FBN SHDN VOU 8V 0.9A 85 80 EFFICIENCY (%) VIN 3.3V L1 4.7μH Efficiency 30.9k LT3479 VREF SS RT GND FBP VC 75 70 65 60 55 4.3k 17.8k 10nF 50 10nF 0 0.2 0.4 0.6 C1: TAIYO YUDEN LMK316BJ225MD C2: AVX 1206 YD106MAT D1: DIODES INC B320A L1: TOKO FDV0630-4R7M 3479 TA03b 5V to –5V/600mA Inverting DC/DC Converter 90 C2 2.2μF D2 C1 2.2μF D1 VIN VS L 100k LT3479 VREF 100pF SS RT 10nF GND 17.8k C3 10μF 402k SW FBP SHDN Efficiency D3 VOUT –5V 600mA 85 80 EFFICIENCY (%) VIN 5V L1 4.7μH 0.8 IOUT (A) 3479 TA05 75 70 65 60 FBN VC 55 1k 15nF 3479 TA06 C1, C2: TAIYO YUDEN LMK316BJ225MD C3: AVX 1206 YD106MAT D1, D2: DIODES INC B320A D3: CENTRAL SEMI, CMDSH-3-LTC L1: TOKO FDV0630-4R7M 50 0 0.2 0.4 0.6 0.8 IOUT (A) 3479 TA04b 3479fb 13 LT3479 TYPICAL APPLICATIONS 500mA, 12 White LED Driver VIN 2.8V TO 4.2V L1 4.7μH D1 C1 2.2μF D2 600mA C2 2.2μF D3 VIN VS L SW ON M1 ON FBN SHDN SS LT3479 VREF 0.15Ω 124k FBP RT GND 10k VC 3479 TA07 10nF 7.5k 10k 2.2nF C1, C2: TAIYO YUDEN LMK316BJ225MD D1: PHILIPS PMEG 2010 D2, D3: LUMILEDS LXHL-PW01 L1: SUMIDA CDRH4D28-4R7 M1: VISHAY SILICONIX Si2302ADS 3479fb 14 LT3479 TYPICAL APPLICATIONS 500mA, 12 White LED Driver L1 10μH VOUT 16V TO 24V D1 C1 4.7μF C2 4.7μF D2 VIN VS L SW 100k FBN SHDN LT3479 SS VREF 93.1k FBP RT 5.9k VC GND 1Ω 10nF 1Ω 10k 17.8k ILED 500mA 3.3nF C1: TAIYO YUDEN EMK316BJ475ML C2: TAIYO YUDEN TMK325BJ475ML D1: DIODES INC B330B D2: LUMILEDS LXHL-NW99 L1: SUMIDA CDRH8D28-100 0.150Ω 3479 TA08 Efficiency 100 VIN = 16V VIN = 12V 90 EFFICIENCY (%) VIN 8V TO 16V VIN = 8V 80 70 60 50 0 0.1 0.2 0.3 IOUT (A) 0.4 0.5 3479 TA08b 3479fb 15 LT3479 TYPICAL APPLICATIONS 8V, 16V, –8V Triple Output Power Supply for TFTLCD Panels D2B VIN 2.8V TO 4.2V C5 0.1μF L1 3.3μH D2A D1 C3 1μF 16V 10mA 8V 700mA C1 4.7μF 100k VIN VS L SW FBN C6 0.1μF SHDN LT3479 VREF GND FBP VC C2 22μF 18.7k SS 10nF RT D3A –8V 10mA 10k 17.8k C4 1μF D3B 2.2nF D1: MBRM120 OR EQUIVALENT D2, D3: BAT54S OR EQUIVALENT L1: SUMIDA CDRH4D28-3R3 C1: AVX 0805ZD475MAT C2: AVX 1210YD226MAT C3 TO C6: X5R/X7R 10V 3479 TA10 Efficiency 100 EFFICIENCY (%) 90 80 70 60 50 0 0.1 0.2 0.3 0.4 0.5 LOAD CURRENT (A) 0.6 0.7 3479 TA10b 3479fb 16 LT3479 TYPICAL APPLICATIONS 1A Dual Tracking Power Supply with Adjustable Outputs 1μF 16V L1 15μH VIN 10V TO 14V 4.7μF 16V D1 VOUT 7V TO 10V 1A L2 15μH VIN VS L 30μF 16V 10.2k SW 470pF SHDN FBN SHDN LT3479 SS VCTRL 0V-2.5V 26.1k VREF 5.76k 1.13k FBP RT VC GND 10nF 4.99k 10.2k 10k 3.3nF 470pF 1μF 16V L3 15μH 4.7μF 16V L4 15μH 30μF 16V D2 VIN VS L SW FBN SHDN SS 11.3k VOUT –7V TO –10V 1A LT3479 VREF FBP RT 20nF GND VC D3 4.99k 10.2k 3.3nF 3479 TA11 D1, D2: DIODES INC DFLS230 2A, 30V D3: PHILIPS 1PS79SB62 L1-L4: SUMIDA CDRH6D38-150 ALL CAPACITORS X5R/X7R DIELECTRIC OR EQUIVALENT Efficiency 80 VIN =14V, VOUT = p10V VIN =10V, VOUT = p7V EFFICIENCY (%) 75 70 VIN = 14V, VOUT = p7V 65 60 55 50 0 0.2 0.4 0.6 IOUT (A) 0.8 1.0 3479 TA11b 3479fb 17 LT3479 PACKAGE DESCRIPTION DE Package 14-Lead Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1708) 0.65 p0.05 3.50 p0.05 1.70 p0.05 2.20 p0.05 (2 SIDES) PACKAGE OUTLINE 0.25 p 0.05 0.50 BSC 3.30 p0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 4.00 p0.10 (2 SIDES) R = 0.20 TYP 3.00 p0.10 (2 SIDES) 8 0.38 p 0.10 14 1.70 p 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) PIN 1 NOTCH (DE14) DFN 1203 7 0.200 REF 1 0.25 p 0.05 0.50 BSC 0.75 p0.05 0.00 – 0.05 3.30 p0.10 (2 SIDES) BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WGED-3) IN JEDEC PACKAGE OUTLINE MO-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 3479fb 18 LT3479 PACKAGE DESCRIPTION FE Package 16-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation BC 4.90 – 5.10* (.193 – .201) 3.58 (.141) 3.58 (.141) 16 1514 13 12 1110 6.60 p0.10 9 2.94 (.116) 4.50 p0.10 6.40 2.94 (.252) (.116) BSC SEE NOTE 4 0.45 p0.05 1.05 p0.10 0.65 BSC 1 2 3 4 5 6 7 8 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) 0.50 – 0.75 (.020 – .030) NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE 0.25 REF 1.10 (.0433) MAX 0o – 8o 0.65 (.0256) BSC 0.195 – 0.30 (.0077 – .0118) TYP 0.05 – 0.15 (.002 – .006) FE16 (BC) TSSOP 0204 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE 3479fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 19 LT3479 TYPICAL APPLICATION Lumiled Driver for Photo Flash with Output Disconnnect VIN 3.3V TO 4.2V L1 4.7μH D1 C1 2.2μF VIN VS L ON C2 2.2μF D2 SW FBN D3 M1 SHDN LT3479 VREF 115k SS RT 10nF GND 7.5k FBP VC ON ILED 500mA/100mA 0.2Ω 2.49k 10k 10k TORCH MODE ILED = 100mA 2.2nF FLASH MODE ILED = 500mA 3479 TA09 C1, C2: TAIYO YUDEN LMK316BJ225MD D1: PHILIPS PMEG2010 D2, D3: LUMILEDS LXHL-PW01 L1: SUMIDA CDRH4D28-4R7 M1: VISHAY SILICONIX Si2302ADS Lumileds Start-Up Lumileds Torch/Flash Transition VOUT 1V/DIV ILED 0.2A/DIV VOUT AC-COUPLED 500mV/DIV INDUCTOR CURRENT 0.5A/DIV 3479 TA09b 0.2ms/DIV 50μs/DIV ILED 500mA m100mA m500mA 3479 TA09c RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1618 Constant Current, Constant Voltage 1.4MHz, High Efficiency Boost Regulator VIN: 1.6V to 18V, VOUT(MAX) = 5.5V, IQ = 2.5mA, ISD = <1μA, QFN16 Package LTC®3216 1A Low Noise High Current LED Charge Pump with Independent Torch/Flash Current Control VIN: 2.9V to 4.4V, VOUT(MAX) = 5.5V, IQ = 300μA, ISD = <1μA, DFN12 Package LTC3436 3A (ISW), 1MHz, 34V Step-Up DC/DC Converter VIN: 3V to 25V, VOUT(MAX) = 34V, IQ = 0.9mA, ISD = <6μA, TSSOP16E Package LTC3453 Synchronous Buck-Boost High Power White LED Driver VIN: 2.7V to 5.5V, VOUT(MAX) = 5.5V, IQ = 2.5mA, ISD = <1μA, QFN16 Package LT3466 Dual Constant Current, 2MHz, High Efficiency White LED Boost Regulator with Integrated Schottky Diode VIN: 2.7V to 24V, VOUT(MAX) = 40V, IQ = 5mA, ISD = <16μA, DFN Package 3479fb 20 Linear Technology Corporation LT 0808 REV B • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2004