Download Datasheet For Lt3519-2 By Linear Technology

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LT3519/LT3519-1/LT3519-2 LED Driver with Integrated Schottky Diode FEATURES n n n n n n n n n n n n n n DESCRIPTION Up to 3000:1 True Color PWM™ Dimming Wide Input Voltage Range Operation from 3V to 30V Transient Protection to 40V Rail-to-Rail LED Current Sense from 0V to 45V 45V, 750mA Internal Switch Internal Schottky Diode Constant-Current and Constant-Voltage Regulation Boost, SEPIC, Buck-Boost Mode or Buck Mode Topology Open LED Protection and Open LED Status Pin Programmable Undervoltage Lockout with Hysteresis Fixed Frequency: 400kHz (LT3519), 1MHz (LT3519-1), 2.2MHz (LT3519-2) Internal Compensation CTRL Pin Provides Analog Dimming Low Shutdown Current: <1μA 16-Lead MSOP Package The LT®3519/LT3519-1/LT3519-2 are fixed frequency step-up DC/DC converters designed to drive LEDs. They feature an internal 45V, 750mA 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 PWM provides up to 3000:1 PWM 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 PWM is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 7199560 and 7321203. APPLICATIONS n n n n Automotive Industrial Constant Current Source Current Limited Constant Voltage Source TYPICAL APPLICATION 4W Boost Automotive LED Driver VOUT 120 1μF 4.7μF SW ANODE CATHODE VIN ISP 2.49Ω 1M 100k SHDN/UVLO 1M 243k VREF ISN 1M LT3519 CTRL FB 38V LED 100mA 29.4k 137k OPENLED GND 80 60 40 20 0 PWM M1 VIN = 6V AND ABOVE 100 LED CURRENT (mA) VIN 6V TO 30V LED Current vs VIN 68μH 0 10 20 30 VIN (V) 3519 TA01b PWM 3519 TA01a 3519fa 1 LT3519/LT3519-1/LT3519-2 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) VIN, OPENLED (Note 3) .............................................40V SHDN/UVLO (Note 4) ...............................................40V SW, ISP , ISN, ANODE, CATHODE ..............................45V PWM, CTRL ..............................................................10V FB, VREF ......................................................................3V Operating Junction Temperature Range (Note 2).................................................. –40°C to 125°C Maximum Junction Temperature........................... 125°C Storage Temperature Range................... –65°C to 125°C TOP VIEW GND OPENLED PWM SHDN/UVLO VIN SW ANODE GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 GND VREF CTRL FB ISN ISP CATHODE GND MS PACKAGE 16-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 130°C/W ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3519EMS#PBF LT3519EMS#TRPBF 3519 16-Lead Plastic MSOP –40°C to 125°C LT3519EMS-1#PBF LT3519EMS-1#TRPBF 35191 16-Lead Plastic MSOP –40°C to 125°C LT3519EMS-2#PBF LT3519EMS-2#TRPBF 35192 16-Lead Plastic MSOP –40°C to 125°C LT3519IMS#PBF LT3519IMS#TRPBF 3519 16-Lead Plastic MSOP –40°C to 125°C LT3519IMS-1#PBF LT3519IMS-1#TRPBF 35191 16-Lead Plastic MSOP –40°C to 125°C LT3519IMS-2#PBF LT3519IMS-2#TRPBF 35192 16-Lead Plastic MSOP –40°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 finish parts. 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/ ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, SHDN/UVLO = 12V, CTRL = 2V, PWM = 5V, unless otherwise noted. PARAMETER CONDITIONS VIN Operating Voltage Range Continuous Operation (Note 3) MIN VIN Supply Current SHDN/UVLO = 0V (Shutdown) PWM = 0V (Idle) PWM > 1.5V, FB = 1.5V (Active, Not Switching) Current Sense Voltage (VISP-VISN) ISP = 24V ISP = 0V l Zero Current Sense Voltage (VISP-VISN) ISP = 24V, CTRL = 100mV l Current Sense Voltage Line Regulation 2.5V < ISP < 45V TYP 3 MAX UNITS 30 V 0.1 2.0 2.5 1 3.0 3.5 μA mA mA 240 250 250 260 mV mV –15 –6 3 mV 0.02 %/V 3519fa 2 LT3519/LT3519-1/LT3519-2 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, SHDN/UVLO = 12V, CTRL = 2V, PWM = 5V, unless otherwise noted. PARAMETER CONDITIONS MIN TYP MAX UNITS Switching Frequency 400kHz (LT3519) 1MHz (LT3519-1) 2.2MHz (LT3519-2) l l l 320 0.80 1.9 400 1 2.2 440 1.10 2.4 kHz MHz MHz Maximum Duty Cycle 400kHz (LT3519) 1MHz (LT3519-1) 2.2MHz (LT3519-2) l l l 94 86 72 97 93 83 l 750 980 Switch Current Limit Switch VCESAT ISW = 500mA Switch Leakage Current SW = 45V, PWM = 0V 1150 300 mA mV 2 CTRL for Full-Scale LED Current CTRL Pin Bias Current % % % μA 1.2 Current Out of Pin, CTRL = 0.1V V 50 PWM Input High Voltage l PWM Input Low Voltage l 100 nA 0.8 V 1.5 PWM Pin Resistance to GND V 70 FB Regulation Voltage (VFB) l FB Pin Threshold Voltage for OPENLED Falling 1.190 1.220 kΩ 1.250 V VFB – 70mV VFB – 60mV VFB – 50mV FB Pin Bias Current Current Out of Pin, FB = 1V ISP , ISN Idle Input Bias Current PWM = 0V, ISP = ISN = 24V ISP , ISN Active Input Bias Current ISP = ISN = 24V, Current per Pin 17 μA Schottky Forward Drop ISCHOTTKY = 500mA 0.8 V Schottky Leakage Current CATHODE = 24V, ANODE = 0V SHDN/UVLO Threshold Voltage Falling 60 V l SHDN/UVLO Input Low Voltage IVIN Drops Below 1μA SHDN/UVLO Pin Bias Current Low SHDN/UVLO = 1.15V SHDN/UVLO Pin Bias Current High SHDN/UVLO = 1.30V VREF Output Voltage –100μA ≤ IVREF ≤ 0μA 1.180 1.8 l 1.96 120 nA 1 μA 4 μA 1.270 V 0.4 V 2.2 2.6 μA 10 100 nA 2 2.04 V 1.220 VREF Output Pin Regulation 3V < VIN < 40V 0.04 %/V OPENLED Output Low (VOL) IOPENLED = 1mA 240 mV OPENLED Leakage Current FB = 0V, OPENLED = 40V 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 0°C to 125°C junction temperature range. Specifications over the –40°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 specifications over the –40°C to 125°C operating junction temperature range. Note 3. Absolute maximum voltage at VIN and OPENLED is 40V for nonrepetitive one second transients and 30V for continuous operation. Note 4. For VIN below 6V, the SHDN/UVLO pin must not exceed VIN for proper operation. 3519fa 3 LT3519/LT3519-1/LT3519-2 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted) Switch Current Limit vs Duty Cycle VISP-VISN Threshold vs VCTRL VIN = 12V VISP = 24V SWITCH CURRENT LIMIT (mA) VISP-VISN THRESHOLD (mV) 250 200 150 100 50 1.0 1.5 2.02 900 600 2.0 1.97 0 25 50 75 DUTY CYCLE (%) 1.96 –50 100 260 1200 250 248 246 244 100 125 Oscillator Frequency vs Temperature (LT3519) 420 VIN = 12V 1100 410 FREQUENCY (kHz) SWITCH CURRENT LIMIT (mA) 254 252 50 75 0 25 TEMPERATURE (°C) 3519 G03 Switch Current Limit vs Temperature VIN = 12V VISP = 24V VCTRL = 2V –25 3519 G02 VISP-VISN Threshold vs Temperature VISP-VISN THREHSOLD (mV) 2.00 1.98 700 3519 G01 256 2.01 1.99 800 VCTRL (V) 258 VIN = 12V 2.03 1000 –50 0.5 2.04 1100 0 0 VREF Voltage vs Temperature 1200 VREF (V) 300 1000 900 800 700 400 390 380 370 242 240 –50 –25 100 50 25 0 75 TEMPERATURE (°C) 600 –50 125 –25 75 0 50 25 TEMPERATURE (°C) VISP-VISN Threshold vs VISP VREF Voltage vs VIN 100 125 Quiescent Current vs VIN 3.0 2.03 256 2.5 254 252 250 248 VIN CURRENT (mA) 2.02 VREF (V) VISP-VISN THRESHOLD (mV) 50 25 75 0 TEMPERATURE (°C) 3519 G06 2.04 VIN = 12V VCTRL = 2V 258 360 –50 –25 125 3519 G05 3519 G04 260 100 2.01 2.00 1.99 246 2.0 1.5 1.0 1.98 244 242 1.97 240 1.96 0 10 30 20 VISP (V) 40 50 0.5 0 5 10 15 20 25 30 35 40 VIN (V) 3519 G07 3519 G08 0 VPWM = 5V VFB = 1.5V 0 10 20 VIN (V) 30 40 3519 G09 3519fa 4 LT3519/LT3519-1/LT3519-2 TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted) FB OPENLED Threshold vs Temperature FB Regulation Voltage vs Temperature 1.25 100 VIN = 12V SHDN/UVLO Threshold vs Temperature 1.30 VIN = 12V 90 VFB-VFB_OPENLED (mV) VFB (V) 1.23 1.22 SHDN/UVLO THRESHLD (V) 80 1.24 70 60 50 40 30 20 1.21 VIN = 12V 1.28 SHDN/UVLO RISING 1.26 1.24 SHDN/UVLO FALLING 1.22 10 1.20 –50 –25 50 25 75 0 TEMPERATURE (°C) 100 0 –50 125 –25 50 25 0 75 TEMPERATURE (°C) 3519 G10 9 300 250 200 150 100 50 600 800 400 SWITCH CURRENT (mA) 1000 8 7 6 5 4 3 2 1 0 –50 –25 50 25 0 75 TEMPERATURE (°C) 3519 G13 125 100 125 800 700 600 500 400 300 200 100 0 0 1000 800 200 600 400 SCHOTTKY FORWARD VOLTAGE DROP (mV) 3519 G14 Oscillator Frequency vs Temperature (LT3519-1) 3519 G15 Oscillator Frequency vs Temperature (LT3519-2) 1.2 2.5 2.4 1.1 1.0 0.9 0.8 0.7 –50 100 Schottky Forward Voltage Drop VR = 24V FREQUENCY (MHz) 200 FREQUENCY (MHz) SWITCH VOLTAGE (V) 350 50 25 75 0 TEMPERATURE (°C) 900 SCHOTTKY FORWARD CURRENT (mA) 450 SCHOTTKY LEAKAGE CURRENT (μA) 10 400 –25 3519 G12 Schottky Leakage Current vs Temperature 500 0 1.20 –50 125 3519 G11 Switch Saturation Voltage (VCESAT) 0 100 2.3 2.2 2.1 2.0 –25 0 25 75 50 TEMPERATURE (°C) 100 125 3519 G16 1.9 –50 –25 0 25 75 50 TEMPERATURE (°C) 100 125 3519 G17 3519fa 5 LT3519/LT3519-1/LT3519-2 PIN FUNCTIONS GND (Pins 1, 8, 9, 16): Power Ground and Signal Ground. Tie to GND plane for best thermal performance. SW (Pin 6): Switch Pin. Connect the inductor at this pin. Minimize the trace at this pin to reduce EMI. OPENLED (Pin 2): Open LED Status Pin. The OPENLED pin asserts if the FB input is greater than the FB regulation threshold minus 60mV (typical). The pin must have an external pull-up resistor to function. When the PWM input is low and the converter is idle, the OPENLED condition is latched to the last valid state when the PWM input was high. When the PWM input goes high again, the OPENLED pin will be updated. This pin may be used to report an open LED fault. ANODE (Pin 7): Internal Schottky Anode Pin. PWM (Pin 3): Pulse Width Modulated Input. A signal low disables the oscillator and turns off the main switch. PWM has an internal pull-down resistor. Tie PWM pin to VREF 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 0.4V or less to disable device and reduce VIN quiescent current below 1μA. Pin may be tied to VIN, but do not tie it to a voltage higher than VIN if VIN is less than 6V. VIN (Pin 5): Input Supply Pin. This pin must be locally bypassed with a 1μF ceramic capacitor (or larger) placed close to it. CATHODE (Pin 10): 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 VISP –VISN increase. ISN (Pin 12): Current Sense Resistor Negative Pin. This input is the inverting input of the internal current sense amplifier. FB (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 FB to 1.22V (nominal) through the DC/DC converter. If the FB input is regulating the loop, the OPENLED pull-down is asserted. This action may signal an open LED fault. Do not leave the FB pin open. If not used, connect to GND. 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 VREF pin or a voltage above 1.2V for full-scale threshold of 250mV, or use a voltage between 0.1V and 1.0V to linearly adjust the threshold. A voltage between 1.0V and 1.2V transitions to the full-scale threshold. Tie CTRL pin to the VREF pin if not used. VREF (Pin 15): Reference Output Pin. Typically 2V. This pin can supply up to 100μA. 3519fa 6 LT3519/LT3519-1/LT3519-2 BLOCK DIAGRAM LED ARRAY COUT RSENSE L1 VIN PWM 11 12 3 + 10 PWM ISN ISP 7 CATHODE 6 ANODE SW D1 – VIN 5 s4 100mV –+ 1.1V 14 CTRL – + + CIN A1 + – A3 + + 1.22V R1 13 FB RC ERROR AMPLIFIER A2 G3 MAIN SWITCH DRIVER CC + – A4 R G1 G2 Q S Q1 MAIN SWITCH PWM COMPARATOR R2 VIN 4 SHDN/UVLO + BANDGAP AND BIAS + 2.2μA – G4 Q3 VIN 15 FB + 1.16V – OSCILLATOR 140μA VREF GND 1, 8, 9, 16 RAMP GENERATOR – 1.22V RS A5 OPENLED Q4 2 IQ4 – 92k 2V + A6 Q2 3519 BD NOTE: THE MAXIMUM ALLOWED Q4 COLLECTOR CURRENT IQ4 IS 2mA. 3519fa 7 LT3519/LT3519-1/LT3519-2 OPERATION The LT3519/LT3519-1/LT3519-2 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 PWM 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 VC node voltage, and forces the converter into either a constant-current or a constant-voltage mode. The LT3519/LT3519-1/LT3519-2 are designed to transition cleanly between these two modes of operation. The current sense amplifier senses the voltage across RSENSE 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 RSENSE and the lower of VCTRL or 1.1V. In this manner, the error amplifier sets the correct peak switch current level to regulate the current through RSENSE. 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 RSENSE can be adjusted by changing the input voltage VCTRL. The FB voltage loop is implemented by the amplifier A2. When the voltage loop dominates, the VC node voltage is set by the amplified difference of the internal reference of 1.22V and the FB pin. If FB voltage is lower than the reference voltage, the switch current will increase; if FB voltage is higher than the reference voltage, the switch demand current will decrease. The LED current sense feedback interacts with the FB voltage feedback so that FB 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, FB can be connected to GND. To deactivate the LED current loop entirely, the ISP and ISN should be tied together and the CTRL input tied to VREF . When the FB input exceeds a voltage about 60mV lower than the FB regulation voltage, the pull-down driver on the OPENLED 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 PWM pin. When the PWM pin is low, switching is disabled and the error amplifier is turned off so that it does not drive the VC node. Also, all internal loads on the VC node are disabled so that the charge state of the VC node will be saved on the internal compensation capacitor. This feature reduces transient recovery time. When the PWM input again transitions high, the demand current for the switch returns to the value just before PWM last transitioned low. To further reduce transient recovery time, an external MOSFET should be used to disconnect the LED array current loop when PWM is low, stopping COUT from discharging. 3519fa 8 LT3519/LT3519-1/LT3519-2 APPLICATIONS INFORMATION Dimming Control There are two methods to control the current source for dimming using the LT3519/LT3519-1/LT3519-2. The first method, PWM Dimming, uses the PWM 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 VC node during the quiescent phase when PWM is low. This feature minimizes recovery time when the PWM signal goes high. To obtain best PWM 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 PWM signal low phase. For best product of analog and PWM dimming, the minimum PWM low or high time should be at least six switching cycles (3μs for fSW = 2MHz). Maximum PWM period is determined by the system. The maximum PWM dimming ratio (PWMRATIO) can be calculated from the maximum PWM period (tMAX) and the minimum PWM pulse width (tMIN) as follows: PWMRATIO = tMAX tMIN When VCTRL is higher than 1.2V, the LED current is clamped to be: ILED = 250mV RSENSE When VCTRL is more than 1V but less than 1.2V, the LED current is in the nonlinear region of VISP-VISN Threshold vs VCTRL 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 VREF 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: ⎛ R1 ⎞ VOUT = ⎜ +1⎟ • 1.22V ⎝ R2 ⎠ Example: tMAX = 9ms, tMIN = 3μs (fSW = 2MHz) PWMRATIO = 9ms = 3000:1 3µs The second method of dimming control, Analog Dimming, uses the CTRL pin to linearly adjust the current sense threshold during the PWM high state. When the CTRL pin voltage is less than 1V but more than 100mV, the LED current is: ILED = VOUT R1 LT3519/ LT3519-1/ FB LT3519-2 R2 3519 F01 Figure 1. FB Resistor Divider for Boost LED Driver VCTRL – 100mV 4 • RSENSE 3519fa 9 LT3519/LT3519-1/LT3519-2 APPLICATIONS INFORMATION For open LED protection of a boost type LED driver, set the resistor from the output to the FB pin such that the expected VFB 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 GND as illustrated in Figure 2. The open LED voltage level can be expressed as: VOUT = VBE(Q1) + R1 • 1.22V R2 + 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: R1+ R2 • 1.22V R2 VIN(RISING) = 2.2µA • R1+ VIN(FALLING) VIN(FALLING) = RSENSE(EXT) R1 V OUT – LT3519/ LT3519-1/ FB LT3519-2 100k VIN LED ARRAY Q1 LT3519/ LT3519-1/ SHDN/UVLO LT3519-2 R1 R2 R2 3519 F02 3519 F03 Figure 2. Open LED Protection FB Resistor Connector for Buck Mode or Buck-Boost Mode LED Driver Figure 3. SHDN/UVLO Threshold Programming 3519fa 10 LT3519/LT3519-1/LT3519-2 APPLICATIONS INFORMATION Inductor Selection The inductor used with the LT3519/LT3519-1/LT3519-2 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 150mA or more. In the buck mode, the inductor value can be estimated using the formula: D • ( VIN – VLED ) ⎛ µH • A • MHz ⎞ L (µH) = BUCK ⎟ ⎜ fOSC (MHz) • 0.15A ⎝ V ⎠ V DBUCK = LED VIN VLED is the voltage across the LED string, VIN is the input voltage to the converter, and fOSC is the switching frequency. In the boost configuration, the inductor can be estimated using the formula: L (µH) = DBOOST • VIN ⎛ µH • A • MHz ⎞ ⎜ ⎟ fOSC (MHz) • 0.15A ⎝ V ⎠ DBOOST = ( VLED – VIN ) VLED Table 1. Recommended Inductor Vendors VENDOR PHONE WEB Sumida (408)321-9660 www.sumida.com Toko (408)432-8281 www.toko.com Cooper (561)998-4100 www.cooperet.com Vishay (402)563-6866 www.vishay.com Input Capacitor Selection For proper operation, it is necessary to place a bypass capacitor to GND close to the VIN pin of the LT3519/ LT3519-1/LT3519-2. 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 ESL and have an adequate ripple current rating. A 2.2μF ceramic type capacitor is usually sufficient for LT3519 (400kHz version). A capacitor of proportionately less value for LT3519-1/LT3519-2 (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 PWM dimming applications may require a larger capacitor value to support the LED voltage during PWM 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)535-2600 www.tdk.com Kemet (408)986-0424 www.kemet.com Murata (814)237-1431 www.murata.com Taiyo Yuden (408)573-4150 www.t-yuden.com 3519fa 11 LT3519/LT3519-1/LT3519-2 APPLICATIONS INFORMATION Open LED Detection Board Layout The LT3519/LT3519-1/LT3519-2 provide an open-collector status pin, OPENLED, that pulls low when the FB pin is within ~60mV of its 1.22V regulated voltage. If the open LED clamp voltage is programmed correctly using the FB pin, then the FB pin should never exceed 1.1V when LEDs are connected, therefore, the only way for the FB pin to be within 60mV of the 1.22V regulation voltage is for an open LED event to have occurred. 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 VIN supply to the LT3519 should be placed as close as possible to the VIN pin and GND. Likewise, place COUT next to the CATHODE pin. Do not extensively route high impedance signals such as FB and CTRL, as they may pick up switching noise. Figure 5 shows the recommended component placement. Inrush Current The LT3519/LT3519-1/LT3519-2 have a built-in Schottky diode for a boost converter. When supply voltage is applied to VIN pin, the voltage difference between VIN and VOUT generates inrush current flowing 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 10A. In addition, the LT3519/LT3519-1/LT3519-2 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 10A, 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. L1 + Diodes, Inc Zetex International Rectifier PART NUMBER VR (V) IAVE (A) DFLS160 60 1 ZLLS10000TA 40 1 10MQ060N 60 1.5 D1 VOUT VIN LOAD 3519 F04 Figure 4. High Frequency Path GND GND VREF OPENLED PWM CTRL SHDN/UVLO FB VIN ISN ISP SW ANODE CATHODE GND GND Table 3. Schottky Diodes Recommended for Hot Plug VENDOR SW L1 RS COUT CIN VIN GND VOUT 3519 F05 Figure 5. Suggested Layout 3519fa 12 LT3519/LT3519-1/LT3519-2 TYPICAL APPLICATIONS 4W Boost Automotive LED Driver VIN 6V TO 30V L1 68μH VOUT C2 4.7μF C1 1μF SW ANODE CATHODE VIN ISP RSENSE 2.49Ω 1M 100k SHDN/UVLO 1M 243k VREF ISN 1M LT3519 FB CTRL 38V LED 100mA 29.4k 137k OPENLED GND PWM M1 C1: TDK C3216X7R1H105K PWM C2: MURATA GRM32ER71H475KA88 L1: COILTRONICS DR74-680-R M1: VISHAY SILICONIX Si2308DS RSENSE: STACKPOLE ELECTRONICS RHC 2512 2.49 5V 3519 TA02a NOTE: VIN = 8.2V RISING TURN ON VIN = 6.2V FALLING UVLO VIN > 10V FULL LED CURRENT AND FOLDBACK BELOW VOUT 42.7V OVERVOLTAGE PROTECTION 1000:1 PWM Dimming at 120Hz Efficiency vs VIN 94 PWM 5V/DIV 92 EFFICIENCY (%) ILED 0.1A/DIV IL 0.3A/DIV VIN = 12V 2μs/DIV 90 88 3519 TA02b 86 84 6 10 14 18 VIN (V) 22 26 30 3519 TA02c 3519fa 13 LT3519/LT3519-1/LT3519-2 TYPICAL APPLICATIONS Buck-Boost Mode 150mA LED Driver 16V LED 150mA RSENSE 1.65Ω VOUT C2 1μF L1 47μH VIN 6V TO 24V C1 1μF 1M VIN SW ANODE SHDN/UVLO 100k 243k 1M VREF ISN LT3519 PWM ISP CATHODE 357k CTRL C3 4.7μF 10k 210k Q1 OPENLED C1: TDK C3216X7R1H105K C2: TDK C3216X7R1H105K C3: TDK C3216X7R1E475K L1: COILTRONICS DR73-470-R Q1: DIODES FMMT555 PNP FB GND 24.3k 3519 TA03a NOTE: VIN = 8.2V RISING TURN ON VIN = 6.2V FALLING UVLO VIN > 7V FULL LED CURRENT AND FOLDBACK BELOW VOUT – VIN 18.5V OVERVOLTAGE PROTECTION Waveform for Open LED Efficiency vs VIN 82 ILED 0.1A/DIV 80 EFFICIENCY (%) 78 VOUT 10V/DIV OPENLED 10V/DIV VIN = 12V 50μs/DIV 3519 TA03b 76 74 72 70 68 66 6 9 12 15 VIN (V) 18 21 24 3519 TA03c 3519fa 14 LT3519/LT3519-1/LT3519-2 TYPICAL APPLICATIONS Buck Mode 500mA LED Driver VIN 12V TO 30V (UP TO 40V TRANSIENT) C1 4.7μF 1M 1M SHDN VIN CATHODE ISP SHDN/UVLO RSENSE 0.5Ω CTRL 100k 191k LT3519 VREF 1.5k ISN 130k M1 OPENLED C2 10μF Q2 9V LED 500mA C1: MURATA GRM32ER71H475KA88 C2: TDK C3216X7R1C106M Q1: DIODES FMMT555 PNP Q2: DIODES FMMT494 NPN L1: COILTRONICS DR73-470-R M1: VISHAY SILICONIX Si2337DS 1k 10k VOUT Q1 L1 47μH SW ANODE GND FB PWM 14.7k 5V PWM 3519 TA04a 2000:1 PWM Dimming at 120Hz Efficiency vs VIN 90 PWM 5V/DIV 88 EFFICIENCY (%) ILED 0.5A/DIV IL 0.3A/DIV VIN = 20V 1μs/DIV 86 84 3519 TA04b 82 80 12 15 18 21 VIN (V) 24 27 30 3519 TA04c 3519fa 15 LT3519/LT3519-1/LT3519-2 TYPICAL APPLICATIONS Boost 150mA LED Driver VIN 6V TO 20V L1 15μH C1 1μF SW ANODE VIN LT3519-1 1M 100k VOUT CATHODE C2 2.2μF ISP RSENSE 1.65Ω SHDN/UVLO 243k ISN VREF 1M 1M CTRL FB 137k 40k 24V LED 150mA • • • OPENLED GND PWM PWM C1: TDK C3216X7R1H105K C2: MURATA GRM31CR71H225KA88 L1: COILTRONICS DR74-150-R M1: VISHAY SILICONIX Si2318DS RSENSE: STACKPOLE ELECTRONICS RHC 2512 2.49 AND 4.99 M1 5V 3519 TA05a NOTE: VIN = 8.2V RISING TURN-ON VIN = 6.2V FALLING UVLO VIN > 10V FULL LED CURRENT AND FOLDBACK BELOW VOUT = 31.7V OVERVOLTAGE PROTECTION 3000:1 PWM Dimming at 120Hz Efficiency vs VIN 94 PWM 5V/DIV 92 EFFICIENCY (%) ILED 0.15A/DIV IL 0.5A/DIV VIN = 12V 0.5μs/DIV 90 88 86 3519 TA05b 84 82 6 8 10 12 14 VIN (V) 16 18 20 3519 TA05c 3519fa 16 LT3519/LT3519-1/LT3519-2 TYPICAL APPLICATIONS Minimum BOM Buck Mode 500mA LED Driver VIN 10V TO 25V C1 2.2μF VIN CATHODE ISP SHDN/UVLO 0.5Ω LT3519-2 100k 1M 130k ISN C2 1μF CTRL 6V LED 500mA 140k VREF 10k VOUT PWM Q1 L1 6.8μH OPENLED SW ANODE GND FB 23.2k C1: C2: Q1: L1: TDK C3216X7R1E225K TDK C1608X7R1C105K DIODES FMMT555 PNP COILTRONICS DR73-068-R 3519 TA06a Waveforms for Open LED Efficiency vs VIN 84 ILED 0.5A/DIV 82 80 EFFICIENCY (%) VIN – VOUT 5V/DIV OPENLED 10V/DIV 78 76 74 VIN = 15V 25μs/DIV 3519 TA06b 72 70 10 13 16 19 VIN (V) 22 25 3519 TA06c 3519fa 17 LT3519/LT3519-1/LT3519-2 PACKAGE DESCRIPTION MS Package 16-Lead Plastic MSOP (Reference LTC DWG # 05-08-1669 Rev Ø) 0.889 p 0.127 (.035 p .005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.305 p 0.038 (.0120 p .0015) TYP 4.039 p 0.102 (.159 p .004) (NOTE 3) 0.50 (.0197) BSC 0.280 p 0.076 (.011 p .003) REF 16151413121110 9 RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) DETAIL “A” 3.00 p 0.102 (.118 p .004) (NOTE 4) 4.90 p 0.152 (.193 p .006) 0o – 6o TYP GAUGE PLANE 0.53 p 0.152 (.021 p .006) DETAIL “A” 0.18 (.007) SEATING PLANE 1.10 (.043) MAX 0.17 – 0.27 (.007 – .011) TYP 1234567 8 0.50 (.0197) BSC NOTE: 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 0.86 (.034) REF 0.1016 p 0.0508 (.004 p .002) MSOP (MS16) 1107 REV Ø 3519fa 18 LT3519/LT3519-1/LT3519-2 REVISION HISTORY REV DATE A Nov 09 DESCRIPTION PAGE NUMBER Updated to Add LT3519-1 and LT3519-2 Parts 1-20 3519fa 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 LT3519/LT3519-1/LT3519-2 TYPICAL APPLICATIONS SEPIC 150mA LED Driver C3 2.2μF L1A 68μH VIN 4V TO 24V • C1 1μF L1B 68μH • VOUT SW ANODE CATHODE VIN ISP C2 4.7μF RSENSE 1.65Ω 1M 100k SHDN/UVLO 1M 432k VREF ISN 1M LT3519 FB CTRL 16V LED 150mA 69.8k 158k OPENLED GND PWM M1 PWM C1: TDK C3216X7R1H105K C2: TDK C3216X7R1E475K C3: TDK C3216X7R1E225K L1: COILTRONICS DRQ74-680-R (COUPLED INDUCTOR) M1: VISHAY SILICONIX Si2318DS NOTE: VIN = 6V RISING TURN ON VIN = 4V FALLING UVLO VIN > 9V FULL LED CURRENT AND FOLDBACK BELOW VOUT 18.5V OVERVOLTAGE PROTECTION 5V 3519 TA07a Efficiency vs VIN Waveforms for LED Shorted to Ground 88 86 IL1A+IL1B 0.2A/DIV EFFICIENCY (%) 84 ILED 0.1A/DIV ILED_SHORTED 0.5A/DIV VIN = 12V 3519 TA07b 50μs/DIV 82 80 78 76 74 4 8 12 16 20 24 VIN (V) 3519 TA07c RELATED PARTS PART NUMBER LT1618 DESCRIPTION Constant-Current, Constant-Voltage 1.24MHz, High Efficiency Boost Regulator LT3466/LT3466-1 Dual Full Function, 2MHz Diodes White LED Step-Up Converter with Built-In Schottkys LT3486 Dual 1.3A White LED Converter with 1000:1 True Color PWM Dimming LT3491 2.3MHz White LED Driver with Integrated Schottky Diode COMMENTS Up to 16 White LEDs, VIN: 1.6V to 18V, VOUT(MAX) = 34V, IQ= 1.8mA, ISD < 1μA, MS Package Up to 20 White LEDs, VIN: 2.7V to 24V, VOUT(MAX) = 39V, DFN/TSSOP-16 Packages Drives Up to 16 100mA White LEDs. VIN: 2.5V to 24V, VOUT(MAX) = 36V, DFN/TSSOP Packages Drives Up to 6 LEDs. VIN: 2.5V to 12V, VOUT(MAX) = 27V, SC70/DFN Packages LT3497 Dual Full Function 2.3MHz LED Driver with 250:1 True Color PWM Dimming with Integrated Schottky Diodes LT3517 Full-Featured LED Driver with 1.5A Switch Current LT3518 Full-Featured LED Driver with 2.3A Switch Current Drives Up to 12 LEDs. VIN: 2.5V to 10V, VOUT(MAX) = 32V, 3mm × 2mm DFN Package VIN: 3V to 40V, VOUT(MAX) = 45V, Dimming = 5.000:1 True Color PWM, ISD < 1μA, 4mm × 4mm QFN and TSSOP Packages VIN: 3V to 40V, VOUT(MAX) = 45V, Dimming = 3.000:1 True Color PWM, ISD < 1μA, 4mm × 4mm QFN and TSSOP Packages LT3591 Constant-Current, 1MHz, High Efficiency White LED Step-Up Converter with Built-in Schottkys Up to 10 White LEDs, VIN: 2.5V to 12V, VOUT(MAX) = 45V, 3mm × 2mm DFN Package 3519fa 20 Linear Technology Corporation LT 1109 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2009