LT3519/LT3519-1/LT LED Driver with Integrated Schottky Diode DESCRIPTION

Transcription

1 FEATURES n Up to 3:1 True Color Dimming n Wide Input Voltage Range Operation from 3V to 3V Transient Protection to 4V n Rail-to-Rail LED Current Sense from V to 45V n 45V, 75mA Internal Switch n Internal Schottky Diode n Constant-Current and Constant-Voltage Regulation n Boost, SEPIC, Buck-Boost Mode or Buck Mode Topology n Open LED Protection and Open LED Status Pin n Programmable Undervoltage Lockout with Hysteresis n Fixed Frequency: 4kHz (LT3519), Hz (LT3519-1), 2.2MHz (LT3519-2) n Internal Compensation n CTRL Pin Provides Analog Dimming n Low Shutdown Current: <1μA n 16-Lead MSOP Package LT3519/LT3519-1/LT LED Driver with Integrated Schottky Diode DESCRIPTION The LT 3519/LT3519-1/LT are fi xed frequency step-up DC/DC converters designed to drive LEDs. They feature an internal 45V, 75mA low side switch and Schottky diode. Combining a traditional voltage feedback and a unique rail-to-rail current sense feedback allows these converters to operate as a constant-voltage source or constant-current source. Internal compensation simplifies applications. These devices feature rail-to-rail LED current sense pins that provide the most flexibility in choosing a converter configuration to drive the LEDs. The LED current is externally programmable with a sense resistor. The external provides up to 3:1 dimming and the CTRL input provides analog dimming. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. True Color is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including and APPLICATIONS n Automotive n Industrial n Constant Current Source n Current Limited Constant Voltage Source TYPICAL APPLICATION 6V TO 3V 1μF 1k 4W Boost Automotive LED Driver 137k 68μH 243k SW ANODE SHDN/UVLO V REF CTRL LT3519 CATHODE ISP ISN 29.4k V OUT 2.49Ω 4.7μF 38V LED 1mA LED CURRENT (ma) LED Current vs = 6V AND ABOVE M TA1a (V) 3519 TA1b 1

2 ABSOLUTE MAXIMUM RATINGS (Note 1), (Note 3)...4V SHDN/UVLO (Note 4)...4V SW, ISP, ISN, ANODE, CATHODE...45V, CTRL...1V, V REF...3V Operating Junction Temperature Range (Note 2)... 4 C to 125 C Maximum Junction Temperature C Storage Temperature Range C to 125 C PIN CONFIGURATION SHDN/UVLO SW ANODE TOP VIEW MS PACKAGE 16-LEAD PLASTIC MSOP T JMAX = 125 C, θ JA = 13 C/W V REF CTRL ISN ISP CATHODE ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3519EMS#PBF LT3519EMS#TRPBF Lead Plastic MSOP 4 C to 125 C LT3519EMS-1#PBF LT3519EMS-1#TRPBF Lead Plastic MSOP 4 C to 125 C LT3519EMS-2#PBF LT3519EMS-2#TRPBF Lead Plastic MSOP 4 C to 125 C LT3519IMS#PBF LT3519IMS#TRPBF Lead Plastic MSOP 4 C to 125 C LT3519IMS-1#PBF LT3519IMS-1#TRPBF Lead Plastic MSOP 4 C to 125 C LT3519IMS-2#PBF LT3519IMS-2#TRPBF Lead Plastic MSOP 4 C to 125 C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based fi nish parts. For more information on lead free part marking, go to: For more information on tape and reel specifi cations, go to: ELECTRICAL CHARACTERISTICS The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T A = 25 C. = 12V, SHDN/UVLO = 12V, CTRL = 2V, = 5V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Voltage Range Continuous Operation (Note 3) 3 3 V Supply Current SHDN/UVLO = V (Shutdown).1 1 μa = V (Idle) ma > 1.5V, = 1.5V (Active, Not Switching) ma Current Sense Voltage (V ISP -V ISN ) ISP = 24V ISP = V l mv mv Zero Current Sense Voltage (V ISP -V ISN ) ISP = 24V, CTRL = 1mV l mv Current Sense Voltage Line Regulation 2.5V < ISP < 45V.2 %/V 2

3 ELECTRICAL CHARACTERISTICS LT3519/LT3519-1/LT The l denotes the specifi cations which apply over the full operating temperature range, otherwise specifi cations are at T A = 25 C. = 12V, SHDN/UVLO = 12V, CTRL = 2V, = 5V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Switching Frequency 4kHz (LT3519) l khz Hz (LT3519-1) l MHz 2.2MHz (LT3519-2) l MHz Maximum Duty Cycle 4kHz (LT3519) l % Hz (LT3519-1) l % 2.2MHz (LT3519-2) l % Switch Current Limit l ma Switch V CESAT I SW = 5mA 3 mv Switch Leakage Current SW = 45V, = V 2 μa CTRL for Full-Scale LED Current 1.2 V CTRL Pin Bias Current Current Out of Pin, CTRL =.1V 5 1 na Input High Voltage l 1.5 V Input Low Voltage l.8 V Pin Resistance to 7 kω Regulation Voltage (V ) l V Pin Threshold Voltage for Falling V 7mV V 6mV V 5mV V Pin Bias Current Current Out of Pin, = 1V 6 12 na ISP, ISN Idle Input Bias Current = V, ISP = ISN = 24V 1 μa ISP, ISN Active Input Bias Current ISP = ISN = 24V, Current per Pin 17 μa Schottky Forward Drop I SCHOTTKY = 5mA.8 V Schottky Leakage Current CATHODE = 24V, ANODE = V 4 μa SHDN/UVLO Threshold Voltage Falling l V SHDN/UVLO Input Low Voltage I VIN Drops Below 1μA.4 V SHDN/UVLO Pin Bias Current Low SHDN/UVLO = 1.15V μa SHDN/UVLO Pin Bias Current High SHDN/UVLO = 1.3V 1 1 na V REF Output Voltage 1μA I VREF μa l V V REF Output Pin Regulation 3V < < 4V.4 %/V Output Low (V OL ) I = 1mA 24 mv Leakage Current = V, = 4V 1 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 LT3519E/LT3519E-1/LT3519E-2 are guaranteed to meet specified performance from C to 125 C junction temperature range. Specifications over the 4 C to 125 C operating junction temperature range are assured by design, characterization and correlation with statistical process controls. The LT3519I/LT3519I-1/LT3519I-2 are guaranteed to meet performance specifi cations over the 4 C to 125 C operating junction temperature range. Note 3. Absolute maximum voltage at and is 4V for nonrepetitive one second transients and 3V for continuous operation. Note 4. For below 6V, the SHDN/UVLO pin must not exceed for proper operation. 3

4 TYPICAL PERFORMANCE CHARACTERISTICS (T A = 25 C unless otherwise noted) V ISP -V ISN THRESHOLD (mv) V ISP -V ISN Threshold vs V CTRL = 12V V ISP = 24V SWITCH CURRENT LIMIT (ma) Switch Current Limit vs Duty Cycle V REF (V) V REF Voltage vs Temperature 2.4 = 12V V CTRL (V) DUTY CYCLE (%) TEMPERATURE ( C) G G G3 V ISP -V ISN THREHSOLD (mv) V ISP- V ISN Threshold vs Temperature = 12V V ISP = 24V V CTRL = 2V TEMPERATURE ( C) 3519 G4 SWITCH CURRENT LIMIT (ma) Switch Current Limit vs Temperature = 12V TEMPERATURE ( C) 3519 G5 FREQUENCY (khz) Oscillator Frequency vs Temperature (LT3519) TEMPERATURE ( C) 3519 G6 V ISP -V ISN THRESHOLD (mv) V ISP- V ISN Threshold vs V ISP V REF Voltage vs Quiescent Current vs V ISP (V) = 12V V CTRL = 2V V REF (V) (V) 4 CURRENT (ma) V = 5V V = 1.5V (V) 3519 G G G9 4

5 TYPICAL PERFORMANCE CHARACTERISTICS (T A = 25 C unless otherwise noted) V (V) Regulation Voltage vs Temperature = 12V TEMPERATURE ( C) 3519 G1 V -V _ (mv) Threshold vs Temperature 5 = 12V TEMPERATURE ( C) 3519 G11 SHDN/UVLO THRESHLD (V) SHDN/UVLO Threshold vs Temperature = 12V SHDN/UVLO RISING SHDN/UVLO FALLING TEMPERATURE ( C) 3519 G12 SWITCH VOLTAGE (V) Switch Saturation Voltage (V CESAT ) SCHOTTKY LEAKAGE CURRENT (μa) Schottky Leakage Current vs Temperature V R = 24V SCHOTTKY FORWARD CURRENT (ma) Schottky Forward Voltage Drop SWITCH CURRENT (ma) TEMPERATURE ( C) SCHOTTKY FORWARD VOLTAGE DROP (mv) 3519 G G G Oscillator Frequency vs Temperature (LT3519-1) 2.5 Oscillator Frequency vs Temperature (LT3519-2) FREQUENCY (MHz) 1..9 FREQUENCY (MHz) TEMPERATURE ( C) TEMPERATURE ( C) 3519 G G17 5

6 PIN FUNCTIONS (Pins 1, 8, 9, 16): Power Ground and Signal Ground. Tie to plane for best thermal performance. (Pin 2): Open LED Status Pin. The pin asserts if the input is greater than the regulation threshold minus 6mV (typical). The pin must have an external pull-up resistor to function. When the input is low and the converter is idle, the condition is latched to the last valid state when the input was high. When the input goes high again, the pin will be updated. This pin may be used to report an open LED fault. (Pin 3): Pulse Width Modulated Input. A signal low disables the oscillator and turns off the main switch. has an internal pull-down resistor. Tie pin to V REF if not used. SHDN/UVLO (Pin 4): Shutdown and Undervoltage Lockout Pin. An accurate 1.22V falling threshold with externally programmable hysteresis detects when power is okay to enable switching. Rising hysteresis is generated by the external resistor divider and an accurate internal 2.2μA pull-down current. Above the 1.25V (nominal) rising threshold (but below 6V), SHDN/UVLO input bias current is sub-μa. Below the falling threshold, a 2.2μA pull-down current is enabled so the user can define the hysteresis with external resistor selection. Tie to.4v or less to disable device and reduce quiescent current below 1μA. Pin may be tied to, but do not tie it to a voltage higher than if is less than 6V. (Pin 5): Input Supply Pin. This pin must be locally bypassed with a 1μF ceramic capacitor (or larger) placed close to it. SW (Pin 6): Switch Pin. Connect the inductor at this pin. Minimize the trace at this pin to reduce EMI. ANODE (Pin 7): Internal Schottky Anode Pin. CATHODE (Pin 1): Internal Schottky Cathode Pin. ISP (Pin 11): Current Sense Resistor Positive Pin. This input is the noninverting input of the internal current sense amplifier. Input bias current increases with V ISP V ISN increase. ISN (Pin 12): Current Sense Resistor Negative Pin. This input is the inverting input of the internal current sense amplifier. (Pin 13): Voltage Loop Feedback Pin. It is used to connect to output resistor divider for constant voltage regulation or open LED protection. The internal transconductance amplifier will regulate to 1.22V (nominal) through the DC/DC converter. If the input is regulating the loop, the pull-down is asserted. This action may signal an open LED fault. Do not leave the pin open. If not used, connect to. CTRL (Pin 14): Current Sense Threshold Voltage Adjustment Pin. This pin sets the threshold voltage across the sense resistor between ISP and ISN. Connect directly to the V REF pin or a voltage above 1.2V for full-scale threshold of 25mV, or use a voltage between.1v and 1.V to linearly adjust the threshold. A voltage between 1.V and 1.2V transitions to the full-scale threshold. Tie CTRL pin to the V REF pin if not used. V REF (Pin 15): Reference Output Pin. Typically 2V. This pin can supply up to 1μA. 6

7 + + BLOCK DIAGRAM LT3519/LT3519-1/LT R SENSE LED ARRAY C OUT L1 11 ISP ISN 3 1 CATHODE D1 7 ANODE 6 SW 5 14 R1 13 R CTRL SHDN/UVLO 2.2μA Q3 V REF 1mV + 1.1V 1.22V 1.22V + + A1 A2 G4 14μA + + A3 ERROR AMPLIFIER BANDGAP AND BIAS R C C C RAMP GENERATOR OSCILLATOR + A4 COMPARATOR G1 R Q S 1.16V G2 + G3 MAIN SWITCH DRIVER A5 + Q1 MAIN SWITCH R S 1, 8, 9, 16 Q4 I Q4 2 C IN 92k A6 Q2 2V + NOTE: THE MAXIMUM ALLOWED Q4 COLLECTOR CURRENT I Q4 IS 2mA BD 7

8 OPERATION The LT3519/LT3519-1/LT are constant frequency, current mode regulators with an internal power switch and Schottky. Operation can be best understood by referring to the Block Diagram. At the start of each oscillator cycle, the SR latch is set, which turns on the Q1 power switch. A voltage proportional to the switch current is added to a stabilizing ramp and the resulting sum is fed into the positive terminal of the comparator, A4. When this voltage exceeds the level at the negative input of A4, the SR latch is reset, turning off the power switch. The level at the negative input of A4 is set by the error amplifier A3. A3 has two inputs, one from the voltage feedback loop and the other one from the current loop. Whichever feedback input is lower takes precedence to set the V C node voltage, and forces the converter into either a constant-current or a constant-voltage mode. The LT3519/LT3519-1/LT are designed to transition cleanly between these two modes of operation. The current sense amplifier senses the voltage across R SENSE and provides an 4 pre-gain to amplifier A1. The output of A1 is simply an amplified version of the difference between the voltage across R SENSE and the lower of V CTRL or 1.1V. In this manner, the error amplifier sets the correct peak switch current level to regulate the current through R SENSE. If the error amplifier s output increases, more current is delivered to the output; if it decreases, less current is delivered. The current regulated in R SENSE can be adjusted by changing the input voltage V CTRL. The voltage loop is implemented by the amplifier A2. When the voltage loop dominates, the V C node voltage is set by the amplified difference of the internal reference of 1.22V and the pin. If voltage is lower than the reference voltage, the switch current will increase; if voltage is higher than the reference voltage, the switch demand current will decrease. The LED current sense feedback interacts with the voltage feedback so that will not exceed the internal reference and the voltage between ISP and ISN will not exceed the threshold set by the CTRL pin. For accurate current or voltage regulation, it is necessary to be sure that under normal operating conditions the appropriate loop is dominant. To deactivate the voltage loop entirely, can be connected to. To deactivate the LED current loop entirely, the ISP and ISN should be tied together and the CTRL input tied to V REF. When the input exceeds a voltage about 6mV lower than the regulation voltage, the pull-down driver on the pin is activated. This function provides a status indicator that the load may be disconnected and the constant-voltage feedback loop is taking control of the switching regulator. Dimming of the LED array is accomplished by pulsing the current using the pin. When the pin is low, switching is disabled and the error amplifier is turned off so that it does not drive the V C node. Also, all internal loads on the V C node are disabled so that the charge state of the V C node will be saved on the internal compensation capacitor. This feature reduces transient recovery time. When the input again transitions high, the demand current for the switch returns to the value just before last transitioned low. To further reduce transient recovery time, an external MOSFET should be used to disconnect the LED array current loop when is low, stopping C OUT from discharging. 8

9 APPLICATIONS INFORMATION Dimming Control There are two methods to control the current source for dimming using the LT3519/LT3519-1/LT The fi rst method, Dimming, uses the pin to modulate the current source between zero and full current to achieve a precisely programmed average current. To make this method of current control more accurate, the switch demand current is stored on the internal V C node during the quiescent phase when is low. This feature minimizes recovery time when the signal goes high. To obtain best dimming performance, it is necessary to use an external disconnect switch in the LED current path to prevent the output capacitor from discharging during the signal low phase. For best product of analog and dimming, the minimum low or high time should be at least six switching cycles (3μs for f SW = 2MHz). Maximum period is determined by the system. The maximum dimming ratio ( RATIO ) can be calculated from the maximum period (t MAX ) and the minimum pulse width (t MIN ) as follows: RATIO = t MAX t MIN Example: t MAX = 9ms, t MIN = 3μs (f SW = 2MHz) RATIO = 9ms 3µs = 3:1 The second method of dimming control, Analog Dimming, uses the CTRL pin to linearly adjust the current sense threshold during the high state. When the CTRL pin voltage is less than 1V but more than 1mV, the LED current is: I LED = V CTRL 1mV 4 R SENSE LT3519/LT3519-1/LT When V CTRL is higher than 1.2V, the LED current is clamped to be: I LED = 25mV R SENSE When V CTRL is more than 1V but less than 1.2V, the LED current is in the nonlinear region of V ISP -V ISN Threshold vs V CTRL as shown in the Typical Performance Characteristics. The LED current programming feature through the CTRL pin possibly increases the total dimming range by a factor of ten. In order to have the accurate LED current, precision resistors are preferred (1% is recommended). The CTRL pin should not be left open. Tie to V REF if not used. Programming Output Voltage (Constant Voltage Regulation) or Open LED/Overvoltage Threshold For a boost application, the output voltage can be set by selecting the values of R1 and R2 (see Figure 1) according to the following equation: V OUT = R1 R V LT3519/ LT3519-1/ LT V OUT R1 R F1 Figure 1. Resistor Divider for Boost LED Driver 9

10 APPLICATIONS INFORMATION For open LED protection of a boost type LED driver, set the resistor from the output to the pin such that the expected V during normal operation will not exceed 1.1V. For a buck mode or buck-boost mode LED driver, the output voltage is typically level-shifted to a signal with respect to as illustrated in Figure 2. The open LED voltage level can be expressed as: V OUT = V BE(Q1) + R1 R2 1.22V Programming the Turn-On and Turn-Off Thresholds with the SHDN/UVLO Pin The falling SHDN/UVLO value can be accurately set by the resistor divider. A small 2.2μA pull-down current is active when SHDN/UVLO is below the 1.22V threshold. The purpose of this current is to allow the user to program the rising hysteresis. The following equations should be used to determine the values of the resistors: (FALLING) = R1+R2 1.22V R2 (RISING) = 2.2µA R1+ (FALLING) LT3519/ LT3519-1/ LT Q1 + R1 V OUT R2 1k R SENSE(EXT) LED ARRAY LT3519/ LT3519-1/ LT SHDN/UVLO R1 R F F3 Figure 2. Open LED Protection Resistor Connector for Buck Mode or Buck-Boost Mode LED Driver Figure 3. SHDN/UVLO Threshold Programming 1

11 APPLICATIONS INFORMATION Inductor Selection The inductor used with the LT3519/LT3519-1/LT should have a saturation current rating of 1A or greater. For buck mode LED drivers, the inductor value should be chosen to give a ripple current 15mA or more. In the buck mode, the inductor value can be estimated using the formula: ( ) LµH ( )= D BUCK V LED µh A MHz f OSC (MHz).15A V D BUCK = V LED V LED is the voltage across the LED string, is the input voltage to the converter, and f OSC is the switching frequency. In the boost configuration, the inductor can be estimated using the formula: LµH ( )= D BOOST f OSC (MHz).15A ( ) D BOOST = V LED V LED Table 1. Recommended Inductor Vendors µh A MHz V VENDOR PHONE WEB Sumida (48) Toko (48) Cooper (561) Vishay (42) Input Capacitor Selection For proper operation, it is necessary to place a bypass capacitor to close to the pin of the LT3519/ LT3519-1/LT A 1μF or greater capacitor with low ESR should be used. A ceramic capacitor is usually the best choice. In the buck mode configuration, the capacitor at the input to the power converter has large pulsed currents. For best reliability, this capacitor should have low ESR and LT3519/LT3519-1/LT ESL and have an adequate ripple current rating. A 2.2μF ceramic type capacitor is usually sufficient for LT3519 (4kHz version). A capacitor of proportionately less value for LT3519-1/LT (higher frequency version) can be used. Output Capacitor Selection The selection of output capacitor depends on the load and converter configuration, i.e., step-up or step-down and the operating frequency. For LED applications, the equivalent resistance of the LED is typically low, and the output filter capacitor should be sized to attenuate the current ripple. To achieve the same LED ripple current, the required filter capacitor value is larger in the boost and buck-boost mode applications than that in the buck mode applications. Lower operating frequencies will require proportionately higher capacitor values. For LED buck mode applications, a 1μF ceramic capacitor is usually sufficient. For the LED boost and buck-boost mode applications, a 2.2μF ceramic capacitor is usually sufficient. Very high performance dimming applications may require a larger capacitor value to support the LED voltage during transitions. Use only ceramic capacitors with X7R, X5R or better dielectric as they are best for temperature and DC bias stability of the capacitor value. All ceramic capacitors exhibit loss of capacitance value with increasing DC voltage bias, so it may be necessary to choose a higher value capacitor to get the required capacitance at the operation voltage. Always check that the voltage rating of the capacitor is sufficient. Table 2. Recommended Ceramic Capacitor Vendors VENDOR PHONE WEB TDK (516) Kemet (48) Murata (814) Taiyo Yuden (48)

12 APPLICATIONS INFORMATION Open LED Detection The LT3519/LT3519-1/LT provide an open-collector status pin,, that pulls low when the pin is within ~6mV of its 1.22V regulated voltage. If the open LED clamp voltage is programmed correctly using the pin, then the pin should never exceed 1.1V when LEDs are connected, therefore, the only way for the pin to be within 6mV of the 1.22V regulation voltage is for an open LED event to have occurred. Inrush Current The LT3519/LT3519-1/LT have a built-in Schottky diode for a boost converter. When supply voltage is applied to pin, the voltage difference between and V OUT generates inrush current fl owing from input through the inductor and the Schottky diode to charge the output capacitor. The selection of inductor and capacitor value should ensure the peak of the inrush current to below 1A. In addition, the LT3519/LT3519-1/LT turn-on should be delayed until the inrush current is less than the maximum current limit. If the peak of the inrush current is more than 1A, an external Schottky diode should be used to bypass both the inductor and internal Schottky. The recommended Schottky diodes for hot plug are shown on Table 3. Table 3. Schottky Diodes Recommended for Hot Plug VENDOR PART NUMBER V R (V) I AVE (A) Diodes, Inc DFLS Zetex ZLLS1TA 4 1 International Rectifier 1MQ6N Board Layout As with all switching regulators, careful attention must be paid to the PCB board layout and component placement. To prevent electromagnetic interference (EMI) problems, proper layout of high frequency switching paths (see Figure 4) is essential. Minimize the length and area of all traces connected to the switching node pin (SW). Keep the sense voltage pins (ISP and ISN) away from the switching node. The bypass capacitor on the supply to the LT3519 should be placed as close as possible to the pin and. Likewise, place C OUT next to the CATHODE pin. Do not extensively route high impedance signals such as and CTRL, as they may pick up switching noise. Figure 5 shows the recommended component placement. + L1 L1 SW D1 V OUT Figure 4. High Frequency Path C IN SHDN/UVLO SW ANODE V REF CTRL ISN ISP CATHODE C OUT LOAD 3519 F4 R S V OUT Figure 5. Suggested Layout 3519 F5 12

13 TYPICAL APPLICATIONS 4W Boost Automotive LED Driver 6V TO 3V C1 1μF L1 68μH SW ANODE CATHODE ISP V OUT C2 4.7μF 1k SHDN/UVLO ISN R SENSE 2.49Ω 137k 243k V REF CTRL LT k 38V LED 1mA C1: TDK C3216X7R1H15K C2: MURATA GRM32ER71H475KA88 L1: COILTRONICS DR74-68-R M1: VISHAY SILICONIX Si238DS R SENSE : STACKPOLE ELECTRONICS RHC NOTE: = 8.2V RISING TURN ON = 6.2V FALLING UVLO > 1V FULL LED CURRENT AND FOLDBACK BELOW V OUT 42.7V OVERVOLTAGE PROTECTION 5V M TA2a 1:1 Dimming at 12Hz Effi ciency vs 94 5V/DIV I LED.1A/DIV I L.3A/DIV EFFICIENCY (%) = 12V 2μs/DIV 3519 TA2b (V) TA2c 13

14 TYPICAL APPLICATIONS Buck-Boost Mode 15mA LED Driver 16V LED 15mA R SENSE 1.65Ω V OUT L1 47μH C2 1μF 6V TO 24V C1 1μF SW ANODE SHDN/UVLO ISN 1k 243k V REF LT3519 ISP CATHODE 21k CTRL Q1 357k 1k C3 4.7μF C1: TDK C3216X7R1H15K C2: TDK C3216X7R1H15K C3: TDK C3216X7R1E475K L1: COILTRONICS DR73-47-R Q1: DIODES FMMT555 PNP 24.3k 3519 TA3a NOTE: = 8.2V RISING TURN ON = 6.2V FALLING UVLO > 7V FULL LED CURRENT AND FOLDBACK BELOW V OUT 18.5V OVERVOLTAGE PROTECTION Waveform for Open LED Effi ciency vs 82 I LED.1A/DIV V OUT 1V/DIV 1V/DIV EFFICIENCY (%) = 12V 5μs/DIV 3519 TA3b (V) TA3c 14

15 TYPICAL APPLICATIONS Buck Mode 5mA LED Driver LT3519/LT3519-1/LT V TO 3V (UP TO 4V TRANSIENT) C1 4.7μF SHDN CATHODE SHDN/UVLO ISP 1k 191k C1: MURATA GRM32ER71H475KA88 C2: TDK C3216X7R1C16M Q1: DIODES FMMT555 PNP Q2: DIODES FMMT494 NPN L1: COILTRONICS DR73-47-R M1: VISHAY SILICONIX Si2337DS CTRL LT3519 V REF ISN M1 9V LED 5mA V OUT R SENSE.5Ω L1 47μH Q2 1.5k 13k 1k C2 1μF 1k Q1 SW ANODE 5V 14.7k 3519 TA4a 2:1 Dimming at 12Hz Effi ciency vs 9 5V/DIV 88 I LED.5A/DIV I L.3A/DIV EFFICIENCY (%) = 2V 1μs/DIV 3519 TA4b (V) TA4c 15

16 TYPICAL APPLICATIONS Boost 15mA LED Driver 6V TO 2V C1 1μF L1 15μH SW ANODE CATHODE V OUT 1k 243k LT SHDN/UVLO V REF ISP ISN R SENSE 1.65Ω C2 2.2μF CTRL 137k 4k 24V LED 15mA C1: TDK C3216X7R1H15K C2: MURATA GRM31CR71H225KA88 L1: COILTRONICS DR74-15-R M1: VISHAY SILICONIX Si2318DS R SENSE : STACKPOLE ELECTRONICS RHC AND 4.99 NOTE: = 8.2V RISING TURN-ON = 6.2V FALLING UVLO > 1V FULL LED CURRENT AND FOLDBACK BELOW V OUT = 31.7V OVERVOLTAGE PROTECTION 5V M TA5a 3:1 Dimming at 12Hz Effi ciency vs 94 5V/DIV 92 I LED.15A/DIV I L.5A/DIV EFFICIENCY (%) = 12V.5μs/DIV 3519 TA5b (V) TA5c 16

17 TYPICAL APPLICATIONS Minimum BOM Buck Mode 5mA LED Driver LT3519/LT3519-1/LT V TO 25V C1 2.2μF CATHODE SHDN/UVLO ISP 1k LT ISN.5Ω 13k 14k CTRL V REF 6V LED 5mA V OUT C2 1μF 1k Q1 L1 6.8μH SW ANODE C1: TDK C3216X7R1E225K C2: TDK C168X7R1C15K Q1: DIODES FMMT555 PNP L1: COILTRONICS DR73-68-R 23.2k 3519 TA6a Waveforms for Open LED 84 Effi ciency vs I LED.5A/DIV 82 8 V OUT 5V/DIV 1V/DIV EFFICIENCY (%) = 15V 25μs/DIV 3519 TA6b (V) 3519 TA6c 25 17

18 PACKAGE DESCRIPTION MS Package 16-Lead Plastic MSOP (Reference LTC DWG # Rev Ø) (.35.5) 5.23 (.26) MIN ( ) (.12.15) TYP.5 (.197) BSC RECOMMENDED SOLDER PAD LAYOUT (.159.4) (NOTE 3) (.11.3) REF.254 (.1) DETAIL A 6 TYP (.193.6) (.118.4) (NOTE 4) GAUGE PLANE.18 (.7) DETAIL A NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE (.21.6) SEATING PLANE 1.1 (.43) MAX (.7.11) TYP (.197) BSC 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED.152mm (.6") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED.152mm (.6") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE.12mm (.4") MAX.86 (.34) REF (.4.2) MSOP (MS16) 117 REV Ø 18

19 REVISION HISTORY REV DATE DESCRIPTION PAGE NUMBER A Nov 9 Updated to Add LT and LT Parts 1-2 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

20 TYPICAL APPLICATIONS SEPIC 15mA LED Driver 4V TO 24V C1 1μF 1k 158k L1A 68μH 432k SW SHDN/UVLO V REF CTRL C3 2.2μF ANODE CATHODE ISP LT3519 L1B 68μH ISN 5V 69.8k R SENSE 1.65Ω M TA7a V OUT 16V LED 15mA C2 4.7μF C1: TDK C3216X7R1H15K C2: TDK C3216X7R1E475K C3: TDK C3216X7R1E225K L1: COILTRONICS DRQ74-68-R (COUPLED INDUCTOR) M1: VISHAY SILICONIX Si2318DS NOTE: = 6V RISING TURN ON = 4V FALLING UVLO > 9V FULL LED CURRENT AND FOLDBACK BELOW V OUT 18.5V OVERVOLTAGE PROTECTION Waveforms for LED Shorted to Ground Effi ciency vs 88 I L1A +I L1B.2A/DIV I LED.1A/DIV I LED_SHORTED.5A/DIV EFFICIENCY (%) = 12V 5μs/DIV 3519 TA7b (V) 3519 TA7c RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1618 Constant-Current, Constant-Voltage 1.24MHz, High Up to 16 White LEDs, : 1.6V to 18V, V OUT(MAX) = 34V, I Q = 1.8mA, Efficiency Boost Regulator I SD < 1μA, MS Package LT3466/LT LT3486 Dual Full Function, 2MHz Diodes White LED Step-Up Converter with Built-In Schottkys Dual 1.3A White LED Converter with 1:1 True Color Dimming Up to 2 White LEDs, : 2.7V to 24V, V OUT(MAX) = 39V, DFN/TSSOP-16 Packages Drives Up to 16 1mA White LEDs. : 2.5V to 24V, V OUT(MAX) = 36V, DFN/TSSOP Packages LT MHz White LED Driver with Integrated Schottky Diode Drives Up to 6 LEDs. : 2.5V to 12V, V OUT(MAX) = 27V, SC7/DFN Packages LT3497 Dual Full Function 2.3MHz LED Driver with 25:1 True Color Dimming with Integrated Schottky Diodes Drives Up to 12 LEDs. : 2.5V to 1V, V OUT(MAX) = 32V, 3mm 2mm DFN Package LT3517 Full-Featured LED Driver with 1.5A Switch Current : 3V to 4V, V OUT(MAX) = 45V, Dimming = 5.:1 True Color, I SD < 1μA, 4mm 4mm QFN and TSSOP Packages LT3518 Full-Featured LED Driver with 2.3A Switch Current : 3V to 4V, V OUT(MAX) = 45V, Dimming = 3.:1 True Color, I SD < 1μA, 4mm 4mm QFN and TSSOP Packages LT3591 Constant-Current, Hz, High Effi ciency White LED Step-Up Converter with Built-in Schottkys Up to 1 White LEDs, : 2.5V to 12V, V OUT(MAX) = 45V, 3mm 2mm DFN Package 2 LT 119 REV A PRINTED IN USA Linear Technology Corporation 163 McCarthy Blvd., Milpitas, CA (48) FAX: (48) LINEAR TECHNOLOGY CORPORATION 29