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LT3519/LT3519-1/LT3519-2

3519fa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

LED Driver with Integrated

Schottky Diode

The LT

3519/LT3519-1/LT3519-2 are ﬁ xed 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 simpliﬁ es

applications. These devices feature rail-to-rail LED current

sense pins that provide the most ﬂ exibility in choosing a

converter conﬁ guration to drive the LEDs. The LED cur-

rent 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.

4W Boost Automotive LED Driver

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

Automotive

Industrial

Constant Current Source

Current Limited Constant Voltage Source

(V)

LED CURRENT (mA)

100

120

10 20 30

3519 TA01b

= 6V AND ABOVE

LED Current vs V

REF

CTRL

SHDN/UVLO

ISP

ISN

OPENLED

ANODE

LT3519

GND

68μH

6V TO 30V

243k

137k

100k

29.4k

2.49Ω

4.7μF

1μF

38V LED

100mA

CATHODE

PWM

3519 TA01a

OUT

Summary of content (20 pages)

PAGE 1
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 wi
PAGE 2
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)........................
PAGE 3
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.
PAGE 4
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 1.97 600 2.0 0 25 50 75 DUTY CYCLE (%) 1.
PAGE 5
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.
PAGE 6
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.
PAGE 7
LT3519/LT3519-1/LT3519-2 BLOCK DIAGRAM LED ARRAY COUT RSENSE L1 VIN PWM 11 12 3 ISN ISP + 10 PWM 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 G1 R Q1 MAIN SWITCH G2 Q S PWM COMPARATOR R2 VIN 4 SHDN/UVLO + BANDGAP AND BIAS + 2.2μA – G4 Q3 VIN FB + 1.16V – OSCILLATOR 140μA 15 GND 1, 8, 9, 16 RAMP GENERATOR – 1.
PAGE 8
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.
PAGE 9
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.
PAGE 10
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.
PAGE 11
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.
PAGE 12
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.
PAGE 13
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 SHDN/UVLO 100k 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.
PAGE 14
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.
PAGE 15
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 1.5k ISN VREF 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.
PAGE 16
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 SHDN/UVLO RSENSE 1.65Ω 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.
PAGE 17
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 130k ISN 1M 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.
PAGE 18
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 .
PAGE 19
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.
PAGE 20
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 ISP VIN C2 4.7μF RSENSE 1.65Ω 1M SHDN/UVLO 100k 1M 432k VREF ISN 1M LT3519 FB CTRL 16V LED 150mA 69.