LT3592 500mA Wide Input Voltage Range Step-Down LED Driver with 10:1 Dimming FEATURES DESCRIPTION n Wide Input Voltage Range The LT®3592 is a fi xed frequency step-down DC/DC con- Operation from 3.6V to 36V verter designed to operate as a constant-current source. n Resistor Adjustable 400kHz–2.2MHz Switching An external sense resistor monitors the output current Frequency allowing accurate current regulation, ideal for driving n Shorted and Open LED Protected high current LEDs. The output current can be dimmed n Internal Switch Current Sense Resistor by a factor of 10 using an external signal for nighttime n External Resistor Programs LED Current, Pin brake lights. Selects 10:1 Ratio The high switching frequency offers several advantages by n 50mA/500mA LED Current Settings permitting the use of a small inductor and small ceramic n Catch Diode Current Sense to Prevent Runaway at capacitors. Small components combined with the LT3592’s High V IN 10-pin DFN leadless surface mount package save space and n Small Thermally Enhanced 10-Lead DFN cost versus alternative solutions. The constant switching (2mm × 3mm) and MSOP-10 Packages frequency combined with low-impedance ceramic capaci- tors result in low, predictable output ripple. APPLICATIONS A wide input voltage range of 3.6V to 36V makes the LT3592 useful in a variety of applications. Current mode n Automotive Signal Lighting PWM architecture provides fast transient response and n Industrial Lighting cycle-by-cycle current limiting. Thermal shutdown provides n Constant-Current, Constant Voltage Supplies additional protection. L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 50/500mA Two Series Red LED Driver Effi ciency for 2 Red LEDs, L = 10μH, 900kHz 100 7V TO 3V2IVN VIN BOOST 95 1μF LT3592 0.1μF 10μH 90 SW BRIGHT 500mA 85 %) DA Y ( 80 CAP + NC 75 BRAOKNE SBHRDIGNHT OUT 200/2–0mV 0.4Ω 4.7μF EFFICIE 70 65 RT 51k 60 140k GND VFB 55 10k 900kHz 50 4 8 12 16 20 24 28 INPUT VOLTAGE (V) 3592 TA01a 3592 TA01b 3592fc 1

LT3592 ABSOLUTE MAXIMUM RATINGS (Note 1) V , BRIGHT Voltages ................................–0.3V to 36V SHDN Voltage ............................................................V IN IN BOOST Voltage .........................................................60V DA Pin Current (Average) .....................–1.2A (sourcing) BOOST above SW pin ...............................................30V Operating Temperature Range (Notes 2, 3) CAP, OUT Voltages (OUT ≤ CAP) ...............................30V LT3592E .............................................–40°C to 125°C V Voltage .................................................................4V LT3592I ..............................................–40°C to 125°C FB R Voltage ...................................................................6V Storage Temperature Range ...................–65°C to 150°C T PIN CONFIGURATION TOP VIEW TOP VIEW RT 1 10 VFB RT 1 10 VFB BRIGHT 2 9 OUT BRIGHT 2 9 OUT SHDN 3 11 8 CAP SHDN 3 11 8 CAP VIN 4 7 BOOST VDIAN 45 76 BSOWOST DA 5 6 SW MSE PACKAGE 10-LEAD PLASTIC MSOP DDB PACKAGE 10-LEAD (3mm (cid:115) 2mm) PLASTIC DFN θJA = 38°C/W, θJC = 8°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB θJA = 76°C/W, θJC = 13.5°C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3592EDDB#PBF LT3592EDDB#TRPBF LDCQ 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C LT3592IDDB#PBF LT3592IDDB#TRPBF LDCQ 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C LT3592EMSE#PBF LT3592EMSE#TRPBF LTDCR 10-Lead Plastic MSOP –40°C to 125°C LT3592IMSE#PBF LT3592IMSE#TRPBF LTDCR 10-Lead Plastic MSOP –40°C to 125°C LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LT3592EDDB LT3592EDDB#TR LDCQ 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C LT3592IDDB LT3592IDDB#TR LDCQ 10-Lead (3mm × 2mm) Plastic DFN –40°C to 125°C LT3592EMSE LT3592EMSE#TR LTDCR 10-Lead Plastic MSOP –40°C to 125°C LT3592IMSE LT3592IMSE#TR LTDCR 10-Lead Plastic MSOP –40°C to 125°C Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/ 3592fc 2

LT3592 ELECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T = 25°C. V = 12V, V = 16V, V = 4V unless otherwise noted. (Note 2) A IN BOOST OUT PARAMETER CONDITIONS MIN TYP MAX UNITS Minimum Input Voltage l 3.25 3.6 V Input Quiescent Current in Shutdown Not Switching 2 3 mA V = 0.3V 0.1 2 μA SHDN CAP to OUT Voltage 0.4Ω CAP to OUT BRIGHT = 1.4V l 190 200 210 mV BRIGHT = 0.3V l 18 20 22 mV DA Pin Current to Stop OSC –0.8 –1 –1.2 A Switching Frequency R = 357k 350 400 450 kHz T R = 140k 800 900 1000 kHz T R = 48.7k 1.9 2.2 2.5 MHz T Maximum Duty Cycle R = 140k 90 94 % T SHDN Input High Voltage 2.3 V SHDN Input Low Voltage 0.3 V BRIGHT Input High Voltage 1.4 V BRIGHT Input Low Voltage 0.3 V Switch Current Limit (Note 4) l 0.85 1.25 1.5 A Switch V I = 500mA 300 mV CESAT SW Boost Pin Current I = 500mA 20 30 mA SW Switch Leakage Current 1 10 μA Minimum Boost Voltage (V – V ) V = 4V 1.8 2.5 V BOOST IN OUT Boost Diode Forward Voltage I = 50mA 800 mV DIO V Voltage OUT = CAP = 4V, Bright = 12V l 1.185 1.21 1.235 V FB V Input Leakage Current V = 1.21V l –250 250 nA FB FB Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 3: This IC includes overtemperature protection that is intended may cause permanent damage to the device. Exposure to any Absolute to protect the device during momentary overload conditions. Junction Maximum Rating condition for extended periods may affect device temperature will exceed the maximum operating junction temperature reliability and lifetime. when overtemperature protection is active. Continuous operation above Note 2: The LT3592E is guaranteed to meet performance specifi cations the specifi ed maximum operating junction temperature may result in from 0°C to 125°C junction temperature. Specifi cations over the –40°C device degradation or failure. to 125°C operating junction temperature range are assured by design, Note 4: Switch Current Measurements are performed when the outputs characterization and correlation with statistical process controls. The are not switching. Slope compensation reduces current limit at higher duty LT3592I is guaranteed over the full –40°C to 125°C operating junction cycles. temperature range. The operating lifetime is derated at junction temperatures greater than 125°C. 3592fc 3

LT3592 TYPICAL PERFORMANCE CHARACTERISTICS (T = 25°C, unless otherwise noted) A Effi ciency (2 Red LEDS, Effi ciency (1 Red LED, Effi ciency (2 Red LEDs, L = 10μH, 900kHz) L = 6.8μH, 900kHz) L = 22μH, 400kHz) 100 100 100 95 95 95 90 90 90 85 BRIGHT (500mA) 85 BRIGHT (500mA) 85 %) 80 %) 80 BRIGHT (500mA) %) Y ( 75 Y ( 75 Y ( 80 C C C N 70 N 70 N 75 EFFICIE 6605 EFFICIE 6605 EFFICIE 70 65 55 55 60 50 50 45 45 55 40 40 50 4 8 12 16 20 24 28 4 8 12 16 20 24 28 4 8 12 16 20 24 28 INPUT VOLTAGE (V) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 3592 G01 3592 G02 3592 G03 Minimum V for 500mA Output Minimum V for 500mA Output IN IN Effi ciency (2 Red LEDs, Current vs V , L = 22μH, Current vs V , L = 6.8μH, OUT OUT L = 4.7μH, 2.2MHz) f = 400kHz (LED Loads) f = 900kHz (LED Loads) 100 12 12 95 11 11 90 10 10 85 BRIGHT (500mA) V) 9 V) 9 NCY (%) 7850 OLTAGE ( 78 OLTAGE ( 78 E V V EFFICI 7605 OUTPUT 65 OUTPUT 65 60 4 4 55 3 3 50 2 2 4 8 12 16 20 24 28 2 4 6 8 10 12 2 4 6 8 10 12 INPUT VOLTAGE (V) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 3592 G04 3592 G05 3592 G06 Minimum V for 500mA Output IN Current vs V , L = 4.7μH, Switch Voltage Drop Switch Voltage Drop at 500mA OUT f = 2.2MHz (LED Loads) vs Switch Current vs Temperature 12 500 400 11 450 375 10 400 V) 9 350 E ( V) V) 350 G 8 m 300 m VOLTA 7 V (SW250 V (SW325 TPUT 6 V – IN200 V – IN300 OU 5 150 4 100 275 3 50 2 0 250 2 4 6 8 10 12 14 16 0 100 200 300 400 500 600 700 800 –50 0 50 100 150 INPUT VOLTAGE (V) SWITCH CURRENT (mA) TEMPERATURE (°C) 3592 G07 3592 G08 3592 G09 3592fc 4

LT3592 TYPICAL PERFORMANCE CHARACTERISTICS (T = 25°C, unless otherwise noted) A Undervoltage Lockout Switching Frequency vs Temperature vs Temperature Current Limit During Soft Start 3.4 2300 1400 2100 RT = 48.7k 1200 V) 1900 A) KOUT ( 3.3 1700 MIT (m1000 UNDERVOLTAGE LOC 3.2 f (kHz)SW111531970000000000 RT = 140k SWITCH CURRENT LI 864000000 200 500 RT = 357k 3.1 300 0 –50 0 50 100 150 –50 –30 –10 10 30 50 70 90 110 130 0.5 1 1.5 2 2.5 TEMPERATURE (°C) TEMPERATURE (°C) VSHDN (V) 3592 G10 3592 G11 3592 G12 Frequency Foldback Switch Current Limit Switch Current Limit 2500 1.4 1.50 RT = 48.7k 1.3 1.45 2000 A) 1.2 A) 1.40 Y (kHz)1500 NT LIMIT ( 1.11 NT LIMIT ( 11..3350 TYPICAL NC RE RE 1.25 UE UR 0.9 UR Q1000 C C 1.20 FRE 500 SWITCH 00..87 SWITCH 11..1150 0.6 1.05 0 0.5 1.00 600 800 1000120014001600180020002200 0 20 40 60 80 100 –50 –30 –10 10 30 50 70 90 110 130 SHDN VOLTAGE (mV) DUTY CYCLE (%) TEMPERATURE (°C) 3592 G13 3592 G14 3592 G15 Operating Waveforms, Operating Waveforms Discontinuous Mode VSW VSW 5V/DIV 5V/DIV VCAP VCAP 10mV/DIV 10mV/DIV AC-COUPLED AC-COUPLED IL IL 500mA/DIV 500mA/DIV 500ns/DIV 3592 G16 500ns/DIV 3592 G17 3592fc 5

LT3592 TYPICAL PERFORMANCE CHARACTERISTICS (T = 25°C, unless otherwise noted) A V vs V V vs V BRIGHT OUT DIM OUT 210 25 24 23 205 V) VBRIGHT (mV) V) 22 m m (UT (UT 21 VDIM (mV) O 200 O 20 V V – – P P 19 A A C C V V 18 195 17 16 190 15 0 2 4 6 8 10 12 0 2 4 6 8 10 12 VOUT (V) VOUT (V) 3592 G18 3592 G19 Boost Diode Voltage vs Current Switching Frequency vs R T 1.0 3000 V) 0.9 VBSTDIO 2500 E ( G LTA 0.8 Hz)2000 O k RD V 0.7 NCY (1500 WA UE R Q O E F 0.6 R1000 E F D O DI 0.5 500 0.4 0 0 50 100 150 200 30 60 90 120150180210240270300330360 DIODE CURRENT (mA) RT (kΩ) 3592 G20 3592 G21 3592fc 6

LT3592 PIN FUNCTIONS R (Pin 1): Programs the frequency of the internal oscillator. capacitor. An internal Schottky is provided for the boost T Connect a resistor from R to ground. Refer to Table 1 or function and an external diode is not needed. An external T the Typical Performance Characteristics for resistor values Schottky diode should be connected between BOOST and that result in desired oscillator frequencies. CAP for single LED applications or whenever a higher BOOST voltage is desired. BRIGHT (Pin 2): Used to program a 10:1 dimming ratio for the LED current. Drive this pin above 1.4V to command CAP (Pin 8): Output of the step-down converter and also maximum intensity or below 0.3V to command minimum an input to the LED current sense amplifi er. Connect the intensity. This pin can be PWMed at 150Hz for brightness fi lter capacitor, inductor, and the top of the external LED control between the 1x and 10x current levels. current sense resistor to this pin. SHDN (Pin 3): Used to shutdown the switching regulator OUT (Pin 9): Drives the LED or LEDs and is the other and the internal bias circuits. This pin can be PWMed at input to the LED current sense amplifi er. Connect this pin 150Hz for brightness control. to the anode of the top LED in the string, the bottom of the external LED current sense resistor, and the top of the V (Pin 4): Supplies current to the LT3592’s internal cir- IN V resistor divider. cuitry and to the internal power switches. Must be locally FB bypassed. For automotive applications, a pi network with a V (Pin 10): The feedback node for the output voltage FB cap from V to GND, a series inductor connected between control loop. Tie this node to a resistor divider between OUT IN V and the power source, and another cap from the far and GND to set the maximum output voltage of the step- IN end of the inductor to GND is recommended. down converter according to the following formula: DA (Pin 5): Allows the external catch diode current to be R1+R2 V =1.21(cid:129) sensed to prevent current runaway, such as when VIN is OUT R2 high and the duty cycle is very low. Connect this pin to the anode of the external catch Schottky diode. where R1 connects between OUT and VFB and R2 connects between V and GND. FB SW (Pin 6): The SW pin is the output of the internal power switch. Connect this pin to the inductor and the cathode Exposed Pad (Pin 11): Ground. The underside exposed of the switching diode. pad metal of the package provides both electrical contact to ground and good thermal contact to the printed circuit BOOST (Pin 7): Provides a drive voltage, higher than the board. The device must be soldered to the circuit board input voltage to the internal bipolar NPN power switch. for proper operation. BOOST will normally be tied to the SW pin through a 0.1μF 3592fc 7

LT3592 BLOCK DIAGRAM L3 L2 BATT C2C C2B C2A 4 VIN BRIGHT BRAKE 2 R CAP 8 + 10R + – RSENSE 9 OUT – BOOST 7 LED1 R1 VFB gm = R6 –– VC R C3 10 Q + Q1 LED2 R2 1.21V S L1 SW 6 D1 C1 GND + – DA 5 REG/UVLO OSC SHDN RT GND 3 1 11 R3 VIN RT C4 3592 BD 3592fc 8

LT3592 OPERATION The LT3592 is a constant frequency, current mode step- error amplifi er output means less output current. Current down LED driver. An internal oscillator that is programmed limit is provided by an active clamp on the V node, and C by a resistor from the R pin to ground enables an RS this node is also clamped to the SHDN pin. Soft-start is T fl ip-fl op, turning on the internal 1.25A power switch Q1. implemented by ramping the SHDN pin using an external An amplifi er and comparator monitor the current fl owing resistor and capacitor. between the V and SW pins, turning the switch off when IN An internal regulator provides power to the control this current reaches a level determined by the voltage at circuitry and also includes an undervoltage lockout to V . An error amplifi er that servos the V node has two C C prevent switching when V is less than 3.25V. If SHDN IN inputs, one from a voltage measurement and one from a is low, the output is disconnected and the input current current measurement. is less than 2μA. An instrumentation amplifi er measures the drop across The switch driver operates from the input of the BOOST an external current sense resistor between the CAP and pin. An external capacitor and internal diode are used to OUT pins and applies a gain of 60 (BRIGHT low for dim generate a voltage at the BOOST pin that is higher than the mode) or 6 (BRIGHT high for bright mode) to this signal input supply, which allows the driver to fully saturate the and presents it to one negative error amp input. The output internal bipolar NPN power switch for effi cient operation. of a external resistor divider between OUT and ground is An external diode can be used to make the BOOST drive tied to the V pin and presented to a second negative error FB more effective at low output voltage. amp input. Whichever input is higher in voltage will end up controlling the loop, so a circuit in which current control The oscillator reduces the LT3592’s operating frequency is desired (as for driving a LED) will be set up such that when the voltage at the OUT pin is low. This frequency the output of the instrumentation amp will be higher than foldback helps to control the output current during startup the V pin at the current level that is desired. The voltage and overload. FB feedback loop will act to limit the output voltage and prevent The anode of the catch diode for the step-down circuit is circuit damage if an LED should go open circuit. connected to the DA pin to provide a direct sense of the The positive input to the error amp is a 1.21V reference, current in this device. If this diode’s current goes above a so the voltage loop forces the V pin to 1.21V and the level set by an internal catch diode current limit circuit, the FB current loop forces the voltage difference between CAP oscillator frequency is slowed down. This prevents current and OUT to be 200mV for BRIGHT mode and 20mV for runaway due to minimum on time limitations at high VIN DIM mode. A rise in the output of the error amplifi er voltages. This function can easily be disabled by tying the results in a increase in output current, and a fall in the DA pin and the catch diode anode to ground. 3592fc 9

LT3592 APPLICATIONS INFORMATION Oscillator The BRIGHT mode current is given by: The frequency of operation is programmed by an external I = 200mV/R BRIGHT SENSE resistor from R to ground. Table 1 shows R values for T T The DIM mode current is 10% of the BRIGHT mode value. commonly used oscillator frequencies, and refer to the Typi- The maximum allowed DC value of the BRIGHT mode cur- cal Performance Characteristics curve for other values. rent is 500mA. When the recommended component values are used in a 900kHz 2 LED application, the transient from Table 1. R Values for Selector Oscillator Frequencies T switching between BRIGHT and DIM currents will be less f R OSC T than 50μs in duration. 400kHz 357k 900kHz 140k The sense resistor used should exhibit a low TC to keep the LED current from drifting as the operating temperature 2.2MHz 48.7k changes. FB Resistor Network The BRIGHT pin can tolerate voltages as high as 36V and The output voltage limit is programmed with a resistor can be safely tied to V even in high voltage applications, IN divider between the output and the VFB pin. This is the but it also has a low threshold voltage (~0.7V) that allows voltage that the output will be clamped to in case the LED it to interface to logic level control signals. goes open circuit. Choose the resistors according to Input Voltage Range R1 = R2([V /1.21V] – 1) OUT The maximum allowed input voltage for the LT3592 is Be sure to choose V such that it does not interfere with OUT 36V. The minimum input voltage is determined by either the operation of the current control loop; it should be set the LT3592’s minimum operating voltage of 3.6V or by at least 10% above the maximum expected LED voltage its maximum duty cycle. The duty cycle is the fraction of for the selected BRIGHT output current. R2 should be 20k time that the internal switch is on and is determined by or less to avoid bias current errors. An optional phase- the input and output voltages: lead capacitor of 22pF between V and V reduces OUT FB light-load ripple. V +V DC= OUT D V –V +V Output Current Selection IN SW D The output current levels are programmed by the value of where VD is the forward voltage drop of the catch diode the external current sense resistor between CAP and OUT. (~0.4V) and VSW is the voltage drop of the internal switch Table 2. Inductor Vendor Information SUPPLIER PHONE FAX WEBSITE Panasonic (800) 344-2112 www.panasonic.com/industrial/components/components.html Vishay (402) 563-6866 (402) 563-6296 www.vishay.com/resistors Coilcraft (847) 639-6400 (847) 639-1469 www.coilcraft.com CoEv Magnetics (800) 227-7040 (650) 361-2508 www.circuitprotection.com/magnetics.asp Murata (814) 237-1431 (814) 238-0490 www.murata.com (800) 831-9172 Sumida USA: (847) 956-0666 USA: (847) 956-0702 www.sumida.com Japan: 81(3) 3607-5111 Japan: 81(3) 3607-5144 TDK (847) 803-6100 (847) 803-6296 www.component.tdk.com TOKO (847) 297-0070 (847) 699-7864 www.tokoam.com 3592fc 10

LT3592 APPLICATIONS INFORMATION (~0.4V at maximum load). This leads to a minimum input the V absolute maximum range (36V) during overload IN voltage of: conditions (short circuit or startup). V +V V = OUT D –V +V Minimum On Time IN(MIN) D SW DC MAX The LT3592 will still regulate the output properly at input voltages that exceed V (up to 36V); however, the with DC = 0.90. IN(MAX) MAX output voltage ripple increases as the input voltage is The maximum input voltage is determined by the absolute increased. maximum ratings of the V and BOOST pins. The con- IN Figure 1 illustrates switching waveforms in a 2.2MHz single tinuous mode operation, the maximum input voltage is red LED application near V = 24V. determined by the minimum duty cycle, which is dependent IN(MAX) upon the oscillator frequency: As the input voltage is increased, the part is required to switch for shorter periods of time. Delays associated with DC = f • 70nsec MIN OSC turning off the power switch dictate the minimum on time V +V V = OUT D –V +V of the part. The minimum on time for the LT3592 is ~70ns. IN(MAX) D SW DC Figure 2 illustrates the switching waveforms when the MIN input voltage is increased to V = 26V. IN Note that this is a restriction on the operating input voltage Now the required on time has decreased below the mini- for continuous mode operation. The circuit will tolerate mum on time of 70ns. Instead of the switch pulse width transient inputs up to the absolute maximum of the V IN becoming narrower to accommodate the lower duty and BOOST pins. The input voltage should be limited to cycle requirement, the switch pulse width remains fi xed at 70ns. In Figure 2, the inductor current ramps up to a value exceeding the load current and the output ripple VOUT increases to about 70mV. The part then remains off until 50mV/DIV the output voltage dips below the programmed value IL 500mA/DIV before it switches again. Provided that the load can tolerate the increases output VSW 20V/DIV voltage ripple and the the components have been properly selected, operation about V is safe and will not dam- 1μs/DIV 3592 F01 IN(MAX) age the part. Figure 3 illustrates the switching waveforms Figure 1. when the input voltage is increased to 36V. VOUT VOUT 50mV/DIV 50mV/DIV IL IL 500mA/DIV 500mA/DIV VSW VSW 20V/DIV 20V/DIV 1μs/DIV 3592 F02 1μs/DIV 3592 F03 Figure 2. Figure 3. 3592fc 11

LT3592 APPLICATIONS INFORMATION As the input voltage increases, the inductor current ramps Characteristics section of this data sheet that show the up more quickly, the number of skipped pulses increases, maximum load current as a function of input voltage and and the output voltage ripple increases. For operation inductor value for several popular output voltages. Low above V , the only component requirement is that inductance may result in discontinuous mode operation, IN(MAX) they be adequately rated for operation at the intended which is acceptable, but further reduces maximum load voltage levels. current. For details of the maximum output current and discontinuous mode operation, see Linear Technology The LT3592 is robust enough to survive prolonged opera- Application Note 44. tion under these conditions as long as the peak inductor current does not exceed 1.2A. Inductor saturation due to Catch Diode high current may further limit performance in this operat- ing regime. Depending on load current, a 500mA to 1A Schottky di- ode is recommended for the catch diode, D1. The diode Inductor Selection and Maximum Output Current must have a reverse voltage rating equal to or greater than the maximum input voltage. The ON Semiconductor A good fi rst choice for the inductor value is: MBRA140T3 and Central Semiconductor CMMSH1-40 are (V +0.2V+V ) good choices, as they are rated for 1A continuous forward OUT D L=1.2A(cid:129) current and a maximum reverse voltage of 40V. ƒ Input Filter Network where V is the forward voltage drop of the catch diode D (~0.4V), f is the switching frequency in MHz and L is in μH. For applications that only require a capacitor, bypass V IN With this value, there will be no subharmonic oscillation for with a 1μF or higher ceramic capacitor of X7R or X5R applications with 50% or greater duty cycle. For low duty type. Y5V types have poor performance over tempera- cycle applications in which V is more than three times ture and applied voltage and should not be used. A 1μF IN V , a good guide for the minimum inductor value is ceramic capacitor is adequate to bypass the LT3592 and OUT will easily handle the ripple current. However, if the input (cid:2)(V (cid:1)V (cid:1)0.2V)(cid:5) (cid:2)(V +0.2V+V )(cid:5) IN OUT OUT D power source has high impedance, or there is signifi cant L=1.7(cid:129) (cid:129) (cid:3) (cid:6) (cid:3) (cid:6) (cid:4) VIN(cid:1)VSW +VD (cid:7) (cid:4) ƒ (cid:7) inductance due to long wires or cables, additional bulk capacitance might be necessary. The can be provided where V is the switch voltage drop (about 0.3V at with a low performance (high ESR) electrolytic capacitor SW 500mA). The inductor’s RMS current rating must be greater in parallel with the ceramic device. than your maximum load current and its saturation current Some applications, such as those in automobiles, may should be about 30% higher. For robust operation in fault require extra fi ltering due to EMI/EMC requirements. In conditions, the saturation current should be above 1.5A. To these applications, very effective EMI fi ltering can be pro- keep effi ciency high, the series resistance (DCR) should be vided by a capacitor to ground right at the source voltage, less than 0.1Ω. Table 2 lists several inductor vendors. a series ferrite bead, and a pi fi lter composed of a capacitor Of course, such a simple design guide will not always re- to ground, a series inductor, and another capacitor directly sult in the optimum inductor for your application. A larger from the device pin to ground (see the Block Diagram for value provides a higher maximum load current and reduces an example). Typical values for the fi lter components are output voltage ripple at the expense of a slower transient 10nF for C2C, a ferrite bead that is ~220Ω at 100MHz for response. If your load is lower than 500mA, then you can L2, 3.3μF for C2B, 10μH for L3, and 1μF for C2A. decrease the value of the inductor and operate with higher Step-down regulators draw current from the input sup- ripple current. This allows you to use a physically smaller ply in pulses with very fast rise and fall times. The input inductor, or one with a lower DCR resulting in higher effi - capacitor is required to reduce the resulting voltage ripple ciency. There are several graphs in the Typical Performance 3592fc 12

LT3592 APPLICATIONS INFORMATION at the LT3592 and to force this very high frequency switch- You can estimate output ripple with the following ing current into a tight local loop, minimizing EMI. A 1μF equation: capacitor is capable of this task, but only if it is placed ΔI close to the LT3592 and catch diode (see the PCB layout V = LP−P RIPPLE 8(cid:129)ƒ(cid:129)C section). A second precaution regarding the ceramic input OUT capacitor concerns the maximum input voltage rating of where ΔI is the peak-to-peak ripple current in the in- the LT3592. A ceramic input capacitor combined with trace LP-P ductor. The RMS content of this ripple is very low, so the or cable inductance forms a high quality (underdamped) RMS current rating of the output capacitor is usually not tank circuit. If the LT3592 circuit is plugged into a live a concern. It can be estimated with the formula: supply, the input voltage can ring to twice its nominal value, possibly exceeding the LT3592’s voltage rating. ΔI I = L This situation can easily be avoided, as discussed in the C(RMS) 12 Hot Plugging Safety section. For more details, see Linear Technology Application Note 88. The low ESR and small size of ceramic capacitors make them the preferred type for LT3592 applications. Not all Output Capacitor ceramic capacitors are the same, though. Many of the higher value ceramic capacitors use poor dielectrics with For most 2.2MHz LED applications, a 3.3μF or higher high temperature and voltage coeffi cients. In particular, output capacitor is suffi cient for stable operation. A Y5V and Z5U types lose a large fraction of their capacitance 900kHz application should use a 4.7μF or higher output with applied voltage and at temperature extremes. capacitor. 400kHz applications require a 22μF or higher output capacitor. The minimum recommended values Because loop stability and transient response depend on should provide an acceptable (if somewhat underdamped) the value of C , this loss may be unacceptable. Use X7R OUT transient response, but larger values can always be used and X5R types. Table 3 lists several capacitor vendors. when extra damping is required or desired. Figure 4 shows the transient response of the LT3592 when The output capacitor fi lters the inductor current to generate switching between DIM and BRIGHT current levels with an output with low voltage ripple. It also stores energy in two output capacitor choices. The output load is two series order to satisfy transient loads and stabilizes the LT3592’s Luxeon K2 Red LEDs, the DIM current is 50mA and the control loop. Because the LT3592 operates at a high fre- BRIGHT current is 500mA, and the circuit is running at quency, minimal output capacitance is necessary. In addition, 900kHz. The upper photo shows the recommended 4.7μF the control loop operates well with or without the presence value. The second photo shows the improved response of signifi cant output capacitor equivalent series resistance resulting from a larger output capacitor. (ESR). Ceramic capacitors, which achieve very low output ripple and small circuit size, are therefore an option. Table 3. Capacitor Vendor Information SUPPLIER PHONE FAX WEBSITE AVX (803) 448-9411 (803) 448-1943 www.avxcorp.com Sanyo (619) 661-6322 (619) 661-1055 www.sanyovideo.com Taiyo Yuden (408) 573-4150 (408) 573-4159 www.t-yuden.com TDK (847) 803-6100 (847) 803-6296 www.component.tdk.com 3592fc 13

LT3592 APPLICATIONS INFORMATION VOUT ILED VSW 100μs/DIV C = 4.7μF VOUT ILED VSW 100μs/DIV 3592 F04 C = 10μF Figure 4. Transient Load Response of the LT3592 with Different Output Capacitors OPTIONAL D2 D2 BOOST C3 BOOST C3 CAP CAP LT3592 SW LT3592 SW BATT VIN BATT VIN GND DA GND DA 3592 F05a 3592 F05b (5a) (5b) Figure 5. Two Circuits for Generating the Boost Voltage BOOST Pin Considerations parallel with the internal Schottky diode, anode to CAP and cathode to BOOST. For outputs between 3.3V and The capacitor C3 and an internal Schottky diode from 12V, the 0.1μF cap and the internal boost diode will be the CAP to the BOOST pin are used to generate a boost effective. For 3V to 3.3V outputs, use a 0.22μF capacitor. voltage that is higher than the input voltage. An external For output between 2.5V and 3V, use a 0.47μF capacitor fast switching Schottky diode (such as the BAS40) can and an external Schottky diode connected as shown in be used in parallel with the internal diode to make this Figure 5a. For lower output voltages, the external boost boost circuit even more effective. In most cases, a 0.1μF diode’s anode can be tied to the input voltage. This con- capacitor works well for the boost circuit. The BOOST pin nection is not as effi cient as the others because the BOOST must be at least 2.5V above the SW pin for best effi ciency. pin current comes from a higher voltage. The user must For output voltages above 12V, use a 0.1μF cap and an also be sure that the maximum voltage rating of the BOOST external boost diode (such as a BAS40) connected in pin is not exceeded. 3592fc 14

LT3592 APPLICATIONS INFORMATION The minimum operating voltage of an LT3592 application this restricts the input range to one-half of the absolute is limited by the undervoltage lockout (UVLO, ~3.25V) and maximum rating of the BOOST pin. by the maximum duty cycle as outlined above. For proper At light loads, the inductor current becomes discontinuous startup, the minimum input voltage is also limited by the and the effective duty cycle can be very high. This reduces boost circuit. If the input voltage is ramped slowly, or the the minimum input voltage to about 400mV above V . CAP LT3592 is turned on with its SHDN pin when the output is At higher load currents, the inductor current is continu- already in regulation, then the boost capacitor might not ous and the duty cycle is limited by the maximum duty be fully charged. Because the boost capacitor is charged cycle of the LT3592, requiring a higher input voltage to with the energy stored in the inductor, the circuit will rely maintain regulation. on some minimum load current to get the boost circuit running properly. This minimum load generally goes to Soft-Start zero once the circuit has started. Figure 6 shows a plot The SHDN pin can be used to soft-start the LT3592, reducing of minimum input voltage needed to start with a 500mA the maximum input current during startup. The SHDN pin output current versus output voltage with LED loads. For is driven through an external RC fi lter to create a voltage LED applications, the output voltage will typically drop ramp at this pin. Figure 7 shows the startup waveforms rapidly after start due to diode heating, but this is not with and without the soft-start circuit. By choosing a large a concern because the voltage to run is lower than the RC time constant, the peak startup current can be reduced voltage to start. The plots show the worst case situation to programmed LED current, with no overshoot. Choose when V is ramping very slowly. For a lower startup IN the value of the resistor so that it can supply 20μA when voltage, the boost diode’s anode can be tied to V , but IN the SHDN pin reaches 2.3V. 12 12 12 11 11 11 10 10 10 9 9 9 V) V) V) E ( 8 E ( 8 E ( 8 G G G A A A LT 7 LT 7 LT 7 O O O D V 6 D V 6 D V 6 E E E L 5 L 5 L 5 4 4 4 3 3 3 2 2 2 2 4 6 8 10 12 2 4 6 8 10 12 2 4 6 8 10 12 14 16 INPUT VOLTAGE (V) INPUT VOLTAGE (V) INPUT VOLTAGE (V) 400kHz, L = 22μH 3592 F06a 900kHz, L = 6.8μH 3592 F06b 2.2MHz, L = 4.7μH 3592 F06c Figure 6. Input Voltage Needed to Start at 500mA Output Current vs LED Voltage 3592fc 15

LT3592 APPLICATIONS INFORMATION LT3592 IL RUN SHDN 500mA/DIV GND VSW 10V/DIV 3592 F07a VOUT 5V/DIV 50μs/DIV RUN 15k LT3592 IL SHDN 500mA/DIV 0.1μF GND VSW 10V/DIV 3592 F07b VOUT 5V/DIV 50μs/DIV Figure 7. To Soft-Start the LT3592, Add a Resistor and Capacitor to the SHDN Pin Shorted and Open LED Protection becomes shorted or the CAP pin is shorted to ground, the peak output current will be limited by the internal switch In case of a shorted LED string or the OUT pin being current limit, which could be as high as 1.5A. shorted to ground by any means, the current loop will help to limit the output current for many conditions, but If an LED goes open circuit, the voltage control loop the switch current may still reach the switch current limit through the R1-R2 resistor divider to FB will take control on some cycles despite the actions of the current loop. and prevent the output voltages from fl ying up close to For some conditions (especially cold), the output current V . Program the desired open circuit voltage to a value IN for shorted OUT will only be limited by the switch current below the absolute maximum for the CAP and OUT pins limit (which can be as high as 1.5A) and the switching but well above the maximum possible forward drop of the frequency foldback that occurs when OUT is close to LED at the programmed BRIGHT current. ground, and the current control loop will have little to no effect. The total power dissipation will be quite low Reversed Input Protection in either case due to the frequency foldback and the fact In some systems, the output will be held high when the that the small current sense resistor will effectively be the input to the LT3592 is absent. This may occur in battery output load for shorted OUT. Peak switch and inductor charging applications or in battery backup systems where currents will be high, but the peaks will be brief and well a battery or some other supply is diode ORed with the separated due to the lowered operating frequency. The LT3592’s output. If the V pin is allowed to fl oat and the IN main concern in this condition is that the output inductor SHDN pin is held high (either by a logic signal or because not saturate and force the switch into an unsafe operating it is tied to V ), then the LT3592’s internal circuitry will IN condition of simultaneous high current and high voltage draw its quiescent current through its SW pin. This is fi ne drop. If the current sense resistor between CAP and OUT if the system can tolerate a few mA in this state. If you 3592fc 16

LT3592 APPLICATIONS INFORMATION D4 VIN VIN SW VOUT LT3592 SHDN GND FB + BACKUP D4: MBR0540 3592 F08 Figure 8. Circuit to Address Reversed Input and Backpowering Issues CLOSING SWITCH SIMULATES HOT PLUG IIN VIN LT3592 VIN IIN + + GND 10A/DIV 1μF VIN 20V/DIV LOW STRAY IMPEDANCE INDUCTANCE 5μs/DIV ENERGIZED DUE TO 6 FEET 32V SUPPLY (2 METERS) OF TWISTED PAIR (9a) VIN LT3592 IIN + + + GND 10A/DIV 10μF 50V 2.2μF VIN 20V/DIV 5μs/DIV (9b) 1Ω LT3592 VIN IIN + + GND 10A/DIV 0.1μF 2.2μF VIN 20V/DIV 5μs/DIV (9c) 3493 F09 Figure 9. A Well Chosen Input Network Prevents Input Voltage Overshoot and Ensures Reliable Operation When the LT3592 is Connected to a Live Supply 3592fc 17

LT3592 APPLICATIONS INFORMATION ground the SHDN pin, the SW pin current will drop to es- is minor, reducing it by less than one half percent for a two sentially zero. However, if the V pin is grounded while red series LED load in BRIGHT mode operating from 32V. IN the output is held high, then parasitic diodes inside the LT3592 can pull large currents from the output through Frequency Compensation the SW pin and the V pin. Figure 8 shows a circuit that IN The LT3592 uses current mode control to regulate the will run only when the input voltage is present and that loop, whether the current control or voltage control loop protects against a shorted or reversed input. is active. This simplifi es loop compensation. In particular, the LT3592 does not require the ESR of the output capaci- Hot Plugging Safely tor for stability, allowing the use of ceramic capacitors The small size, robustness, and low impedance of ceramic to achieve low output ripple and small circuit size. A low capacitors make them an attractive option for the input ESR output capacitor will typically provide for a greater bypass capacitor of LT3592 circuits. However, these capaci- margin of circuit stability than an otherwise equivalent tors can cause problems if the LT3592 is plugged into a capacitor with higher ESR, although the higher ESR will live supply (see Linear Technology Application Note 88 for tend to provide a faster loop response. Figure 10 shows a complete discussion). The low loss ceramic capacitor an equivalent circuit for the LT3592 control loops, both for combined with stray inductance in series with the power current and voltage mode. Both use the same error amplifi er source forms an underdamped tank circuit, and the volt- and power section, but an additional voltage gain amp is age at the V pin of the LT35392 can ring to twice the used in conjuction with the external current sense resistor IN nominal input voltage, possibly exceeding the LT3592’s to implement output current control. The error amplifi er is rating and damaging the part. If the input supply is poorly a transconductance type with fi nite output impedance. The controlled or the user will be plugging the LT3592 into an power section, consisting of the modulator, power switch, energized supply, the input network should be designed and inductor, is modeled as a transconductance amplifi er to prevent this overshoot. generating an output current proportional to the voltage at the V node. Note that the output capacitor integrates Figure 9 shows the waveforms that result when an LT3592 C this current, and that the capacitor on the V node (C ) circuit is connected to a 32V supply through six feet of 24 C C integrates the error amplifi er output current, resulting in gauge twisted pair. The fi rst plot is the response with a 1μF ceramic capacitor at the input. The input voltage rings as high as 56V and the input current peaks at 16A. gm = 0.7A/V – 0.7V One method of damping the tank circuit is to add another SW capacitor with a series resistor to the circuit. In Figure 9b, + + a tantalum chip capacitor has been added. This capacitor’s C1 BRIGHT C1 high equivalent series resistance (ESR) damps the circuit ESR 30k and eliminates the voltage overshoot. The extra capacitor CAP – improves low frequency ripple fi ltering and can slightly 300k improve the effi ciency of the circuit, thought it is likely RSENSE OUT + to be the largest component in the circuit. An alternate RL R1 gm = 1/5k – solution is shown in Figure 9c. A 1Ω resistor is added in VFB – VC series with the input to eliminate the voltage overshoot R2 1.2V + RC (it also reduces the peak input current). A 0.1μF capacitor gm = 300μA/V CC improves high frequency fi ltering. This solution is smaller GND and less expensive than the tantalum capacitor. For high 3592 F10 input voltages, the impact of the 1Ω resistor on effi ciency Figure 10. Model for Loop Response 3592fc 18

LT3592 APPLICATIONS INFORMATION two poles in the loop. Rc provides a zero. With the recom- terminal of the output capacitor C1). The SW and BOOST mended output capacitor, the loop crossover occurs above nodes should be as small as possible. Finally, keep the the R C zero. This simple model works well as long as the FB node small so that the ground pin and ground traces C C value of the inductor is not too high and the loop crossover will shield it from the SW and BOOST nodes. Include vias frequency is much lower than the switching frequency. near the exposed GND pad of the LT3592 to help remove With a larger ceramic capacitor that will have lower ESR, heat from the LT3592 to the ground plane. crossover may be lower and a phase lead capacitor (C ) PL across the feedback divider may improve the transient High Temperature Considerations response. Large electrolytic capacitors may have an ESR The die temperature of the LT3592 must be lower than the large enough to create an additional zero, and the phase maximum rating of 125°C. This is generally not a concern lead might not be necessary. If the output capacitor is unless the ambient temperature is above 85°C. For higher different than the recommended capacitor, stability should temperatures, extra care should be taken in the layout of be checked across all operating conditions, including DIM the circuit to ensure good heat sinking at the LT3592. The and BRIGHT current modes, voltage control via FB, input maximum load current should be derated as the ambient voltage, and temperature. temperature approaches 125°C. The die temperature is calculated by multiplying the LT3592 power dissipation PCB Layout by the thermal resistance from junction to ambient. For proper operation and minimum EMI, care must be taken Power dissipation within the LT3592 can be estimated during printed circuit board layout. Figure 11 shows the by calculating the total power loss from an effi ciency recommended component placement with trace, ground measurement and subtracting the catch diode loss. The plane, and via locations. Note that large, switched currents resulting temperature rise at full load is nearly independent fl ow in the LT3592’s V and SW pins, the catch diode (D1), of input voltage. Thermal resistance depends upon the IN and the input capacitor (C2). The loop formed by these layout of the circuit board, but 76°C/W is typical for the components should be as small as possible and tied to 3mm × 2mm DFN (DDB10) package, and 38°C/W is typical system ground in only one place. These components, along for the MS10E package. with the inductor and output capacitor, should be placed on the same side of the circuit board, and their connections Higher Output Voltages should be made on that layer. Place a local, unbroken ground At higher output voltages, the choice of output capacitor plane below these components, and tie this ground plane becomes especially critical. Many small case size ceramic to system ground at one location (ideally at the ground capacitors lose much of their rated capacitance well below BRIGHT SHDN VIN SYS GND 3592 F11 Figure 11. A Good PCB Layout Ensures Proper, Low EMI Operation 3592fc 19

LT3592 APPLICATIONS INFORMATION their maximum voltage capability. If a capacitor with a 900kHz with a 6.8μH inductor and a 4.7μF ceramic output lower voltage rating is found to not be stable in a design, capacitor. The LT3592 is in BRIGHT (500mA) mode but it will often result in a smaller solution to choose a larger the current load is switched from 50mA to 450mA and capacitor value of the same voltage rating than to choose back, so the current control loop is not active for either one of the same capacitance and higher voltage rating. For current level and the output voltage is regulated through example, a 10μF, 10V ceramic capacitor might be smaller the resistive voltage divider to the FB pin. than a 4.7μF, 16V part, if a 4.7μF, 10V capacitor is found to not be adequate in a given application. The LT3592HV Other Linear Technology Publications can tolerate sustained output voltages of up to 25V. For Application Notes AN19, AN35, and AN44 contain more output voltages above 12V, use an external Schottky diode detailed descriptions and design information for Step-down for the boost circuit with the anode tied to CAP and the regulators and other switching regulators. The LT1376 data cathode tied to BOOST (as shown in Figure 13). sheet has an extensive discussion of output ripple, loop compensation, and stability testing. Design Note DN100 Transient Performance with Voltage Control Loop shows how to generate a bipolar output supply using a The voltage control loop transient characteristics are similar Step-down regulator. to, but not identical to the current control loop. Figure 12 shows the transient for a 12V input application running at ILED 200mA/DIV VOUT 1V/DIV VSW 10V/DIV 10μs/DIV 3592 F12 Figure 12. Switching Transient When Going from 50mA to 500mA Current and Back in Voltage Mode D2 BOOST C3 CAP LT3592 SW BATT VIN GND DA 3592 F13 Figure 13. Boost Circuit with External Schottky Diode for Output Voltages Above 12V 3592fc 20

LT3592 TYPICAL APPLICATIONS Single Red LED Driver with Boost Diode to V Due to Low V IN OUT 1N4148 5V TO 1V6IVN VIN BOOST 1μF LT3592 0.1μF 15μH SW MBRA120 DA CAP OFF ON SHDN 0.4Ω 22μF FAULT BRIGHT OUT RT 30k LUXEON GND VFB LXK2-PD12-S00 357k 10k 400kHz 3592 TA02 50mA/500mA Two Series Red LED Driver BEAD 10μH 8V TO 3V2IVN VIN BOOST 10nF 3.3μF 1μF LT3592 0.1μF 6.8μH SW CMMSHI-40 DA CAP + OFF ON SHDN 200/20mV 0.4Ω 4.7μF – BRAKE BRIGHT OUT RT 51k 48.7k GND VFB LUXEON 2.2MHz 10k LXK2-PD12-S00 3592 TA03 5V Supply with 500mA Current Limit 8V TO 3V2IVN VIN BOOST 1μF 0.1μF 6.8μH SW LT3592 MBRA140 DA ON SHDN CAP 0.4Ω 4.7μF BRIGHT OUT 5V 31.6k RT GND VFB 48.7k 10k 2.2MHz 3592 TA04 3592fc 21

LT3592 PACKAGE DESCRIPTION DDB Package 10-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1722 Rev Ø) 0.64 ±0.05 3.00 ±0.10 R = 0.115 0.40 ± 0.10 (2 SIDES) R = 0.05 TYP (2 SIDES) TYP 6 10 0.70 ±0.05 2.55 ±0.05 2.00 ±0.10 1.15 ±0.05 PIN 1 BAR (2 SIDES) PIN 1 TOP MARK R = 0.20 OR PACKAGE (SEE NOTE 6) 0.64 ± 0.05 0.25 × 45° OUTLINE (2 SIDES) 5 1 CHAMFER 0.25 ± 0.05 0.200 REF 0.75 ±0.05 0.25 ± 0.05 (DDB10) DFN 0905 REV Ø 0.50 BSC 0.50 BSC 2.39 ±0.05 2.39 ±0.05 (2 SIDES) (2 SIDES) 0 – 0.05 RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229 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 3592fc 22

LT3592 PACKAGE DESCRIPTION MSE Package 10-Lead Plastic MSOP (Reference LTC DWG # 05-08-1664) BOTTOM VIEW OF EXPOSED PAD OPTION 2.06(cid:112) 0.102 2(..719140(cid:112)(cid:112) 0.0.10042) 0(..808395(cid:112)(cid:112) 0.0.10257) 1 (.081(cid:112) .004) 0.29 1.83(cid:112) 0.102 REF (.072(cid:112) .004) 5.23 0.05 REF 2.083(cid:112) 0.102 3.20 – 3.45 (.206) (.082(cid:112) .004) (.126 – .136) DETAIL “B” MIN CORNER TAIL IS PART OF DETAIL “B” THE LEADFRAME FEATURE. FOR REFERENCE ONLY 10 NO MEASUREMENT PURPOSE 0.305(cid:112) 0.038 0.50 3.00(cid:112) 0.102 (.0120(cid:112) .0015) (.0197) (.118(cid:112) .004) 0.497(cid:112) 0.076 TYP BSC (NOTE 3) (.0196(cid:112) .003) RECOMMENDED SOLDER PAD LAYOUT 10 9 8 76 REF 4.90(cid:112) 0.152 3.00(cid:112) 0.102 (.193(cid:112) .006) (.118(cid:112) .004) (NOTE 4) DETAIL “A” 0.254 (.010) 0(cid:111) – 6(cid:111) TYP GAUGE PLANE 1 2 3 4 5 0.53(cid:112) 0.152 1.10 0.86 (.021(cid:112) .006) (.043) (.034) MAX REF DETAIL “A” 0.18 (.007) SEATING PLANE 0.17 – 0.27 0.1016(cid:112) 0.0508 (.007 – .011) (.004(cid:112) .002) 0.50 TYP (.0197) MSOP (MSE) 0908 REV C NOTE: BSC 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 3592fc Information furnished by Linear Technology Corporation is believed to be accurate and reliable. 23 However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

LT3592 TYPICAL APPLICATIONS Five White LED Driver with External Booste Diode 24V TO 3V6IVN VIN BOOST 1μF LT3592 0.1μF 33μH BAS40 SW MBRA140 DA CAP OFF ON SHDN 0.4Ω 4.7μF BRIGHT BRIGHT OUT RT 158k GND VFB 140k 900kHz 10k WHITE LEDs 3592 TA05 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1932 Constant Current, 1.2MHz, High Effi ciency White LED Boost V = 1V, V = 10V, V = 34V, Dimming Analog/PWM, IN(MIN) IN(MAX) OUT(MAX) Regulator I < 1μA, ThinSOT™ Package SD LT3465/ Constant Current, 1.2MHz/2.7MHz, High Effi ciency White LED V = 2.7V, V = 16V, V = 34V, Dimming Analog/PWM, IN(MIN) IN(MAX) OUT(MAX) LT3465A Boost Regulator with Integrated Schottky Diode I < 1μA, ThinSOT Package SD LT3466/ Dual Constant Current, 2MHz, High Effi ciency White LED V = 2.7V, V = 24V, V = 40V, Dimming 5mA, IN(MIN) IN(MAX) OUT(MAX) LT3466-1 Boost Regulator with Integrated Schottky Diode ISD < 16μA, 3mm × 3mm DFN-10 Package LT3474/ 36V, 1A (I ), 2MHz,Step-Down LED Driver V = 4V, V = 36V, V = 13.5V, Dimming 400:1 True LED IN(MIN) IN(MAX) OUT(MAX) LT3474-1 Color PWM, I < 1μA, TSSOP-16E Package SD LT3475/ Dual 1.5A(I ), 36V, 2MHz,Step-Down LED Driver V = 4V, V = 36V, V = 13.5V, Dimming 3,000:1 True LED IN(MIN) IN(MAX) OUT(MAX) LT3475-1 Color PWM, I < 1μA, TSSOP-20E Package SD LT3476 Quad Output 1.5A, 2MHz High Current LED Driver with V = 2.8V, V = 16V, V = 36V, Dimming 1,000:1 True IN(MIN) IN(MAX) OUT(MAX) 1,000:1 Dimming Color PWM, ISD < 10μA, 5mm × 7mm QFN-10 Package LT3478/ 4.5A, 2MHz High Current LED Driver with 3,000:1 Dimming V = 2.8V, V = 36V, V = 40V, Dimming 1,000:1 True IN(MIN) IN(MAX) OUT(MAX) LT3478-1 Color PWM, ISD < 10μA, 5mm × 7mm QFN-10 Package LT3486 Dual 1.3A , 2MHz High Current LED Driver V = 2.5V, V = 24V, V = 36V, Dimming 1,000:1 True IN(MIN) IN(MAX) OUT(MAX) Color PWM, ISD < 1μA, 5mm × 3mm DFN, TSSOP-16E Package LT3491 Constant Current, 2.3MHz, High Effi ciency White LED Boost V = 2.5V, V = 12V, V = 27V, Dimming 300:1 True IN(MIN) IN(MAX) OUT(MAX) Regulator with Integrated Schottky Diode Color PWM, ISD < 8μA, 2mm × 2mm DFN-6, SC70 Package LT3496 Triple Output 750mA, 2.1MHz High Current LED Driver with V = 3V, V = 30V, V = 40V, Dimming 3,000:1 True IN(MIN) IN(MAX) OUT(MAX) 3,000:1 Dimming Color PWM, ISD < 1μA, 4mm × 5mm QFN-28 Package LT3497 Dual 2.3MHz, Full Function LED Driver with Integrated V = 2.5V, V = 10V, V = 32V, Dimming 250:1 True IN(MIN) IN(MAX) OUT(MAX) Schottkys and 250:1 True Color PWM Dimming Color PWM, ISD < 12μA, 2mm × 3mm DFN-10 Package LT3498 20mA LED Driver and OLED Driver Integrated Schottkys V = 2.5V, V = 12V, V = 32V, Dimming Analog/PWM, IN(MIN) IN(MAX) OUT(MAX) ISD < 8.5μA, 2mm × 3mm DFN-10 Package LT3517 1.3A, 2.5MHz High Current LED Driver with 3,000:1 Dimming V = 3V, V = 30V, Dimming 3,000:1 True Color PWM, IN(MIN) IN(MAX) ISD < 1μA, 4mm × 4mm QFN-16 Package LT3518 2.3A, 2.5MHz High Current LED Driver with 3,000:1 Dimming V = 3V, V = 30V, Dimming 3,000:1 True Color PWM, IN(MIN) IN(MAX) ISD < 1μA, 4mm × 4mm QFN-16 Package LT3590 48V, 850kHz, 50mA Step-Down LED Driver VIN(MIN) = 4.5V, VIN(MAX) = 50V, Dimming 0.4, ISD < 15μA, 2mm × 2mm DFN-6, SC70 Package LT3591 Constant Current, 1MHz, High Effi ciency White LED Boost V = 2.5V, V = 12V, V = 40V, Dimming 80:1 True IN(MIN) IN(MAX) OUT(MAX) Regulator with Integrated Schottky Diode and 80:1 True Color Color PWM, ISD < 9μA, 3mm × 2mm DFN-8 Package PWM Dimming ThinSOT is a trademark of Linear Technology Corporation. 3592fc 24 Linear Technology Corporation LT 0409 REV C • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2008