LT3922-1 36V, 2.3A Synchronous Step-Up LED Driver with 25,000:1 PWM Dimming FEATURES DESCRIPTION n 2.5% LED Current Regulation The LT 3922-1 is a monolithic, synchronous, step-up DC/ n 2% Output Voltage Regulation DC converter that utilizes fixed-frequency, peak current n control and provides PWM dimming for a string of LEDs. 25,000:1 PWM Dimming at 100Hz n The LED current is programmed by an analog voltage or 128:1 Internal PWM Dimming n the duty cycle of pulses at the CTRL pin. The LT3922-1 Spread Spectrum Frequency Modulation n will maintain 2.5% current regulation through an external Silent Switcher Architecture for Low EMI n sense resistor over a wide range of output voltages. Operates in Boost, Buck Mode and Buck-Boost Mode n 2.8V to 36V Input Voltage Range The switching frequency is programmable from 200kHz n Up to 34V LED String Voltage to 2MHz by an external resistor at the RT pin or by an n 2.3A, 40V Internal Switches external clock applied at the SYNC/SPRD pin. With the n 200kHz to 2MHz Switching Frequency with SYNC optional spread spectrum frequency modulation enabled, n Analog or Duty Cycle LED Current Control the frequency varies from 100% to 125% to reduce EMI. n Open/Short LED Protection and Fault Indication The LT3922-1 also includes a driver for an external high n Thermally Enhanced 28-Lead (4mm 5mm) QFN side PMOS for PWM dimming and an internal PWM signal n AEC-Q100 Qualified for Automotive Applications generator for analog control of PWM dimming. When an external signal is available, the LT3922-1 can perform 25,000:1 PWM dimming with 100Hz PWM pulses. APPLICATIONS Additional features include an accurate external reference n Automotive and Industrial Lighting voltage for use with the CTRL and PWM pins, an LED n Machine Vision current monitor, an accurate EN/UVLO pin threshold, All registered trademarks and trademarks are the property of their respective owners. Protected open-drain fault reporting for open-circuit and short-circuit by U.S. patents, including 7199560, 7321203, and other patents pending. load conditions, and thermal shutdown. TYPICAL APPLICATION 30V, 333mA Boost LED Driver with 25,000:1 PWM Dimmming L1, 2.2H 33F V IN SW BST V V IN OUT 8V TO 27V 0.47F 4.7F 1M GND EN/UVLO 0.47F 365k V OUT I LED OVLO 1M 100mA/DIV LT3922-1 59.0k 10F FB 33.2k GND V REF V PWM 1F ISP CTRL 2V/DIV PWM 300m SYNC/SPRD ISN INTV CC 200ns/DIV INFINITE PERSISTENCE 100k PWMTG M1 39221 TA01b V = 12V IN FAULT ISMON f = 100Hz PWM SS RT RP V C 2.2F 30V 333mA 51k 45.3k 10nF LED 2MHz 1nF L1: WURTH 74437324022 39221 TA01a M1: VISHAY Si2319CDS Rev. A 1 Document Feedback For more information www.analog.comLT3922-1 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW V and EN/UVLO ......................................................40V IN ISP, ISN, and V ....................................................40V OUT 28 27 26 25 24 23 ISP ISN .................................................................0.3V SW 1 22 GND CTRL and FB ............................................................3.3V BST 2 21 V OUT OVLO, PWM, SYNC/SPRD, and FAULT ........................6V INTV 3 20 PWMTG CC SS and V ................................................................3.3V C V 4 19 PWM IN 29 SW, BST, INTV , V , ISMON, PWMTG, RT, and RP (Note 2) GND CC REF EN/UVLO 5 18 RP Operating Junction Temperature Range (Notes 3, 4) OVLO 6 17 SYNC/SPRD V 7 16 RT LT3922E-1/LT3922I-1 ............................ 40 to 125C REF CTRL 8 15 FAULT LT3922H-1 .............................................40 to 150C 9 10 11 12 13 14 Storage Temperature Range ......................60 to 150C UFD PACKAGE 28-LEAD (4mm 5mm) PLASTIC QFN = 25C/W (AS MEASURED ON DEMO BOARD DC2247A), = 3.4C/W JA JC EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3922EUFD-1 PBF LT3922EUFD-1 TRPBF 39221 28-Lead (4mm 5mm) Plastic QFN 40C to 125C LT3922IUFD-1 PBF LT3922IUFD-1 TRPBF 39221 28-Lead (4mm 5mm) Plastic QFN 40C to 125C LT3922HUFD-1 PBF LT3922HUFD-1 TRPBF 39221 28-Lead (4mm 5mm) Plastic QFN 40C to 150C AUTOMOTIVE PRODUCTS** LT3922EUFD-1 WPBF LT3922EUFD-1 WTRPBF 39221 28-Lead (4mm 5mm) Plastic QFN 40C to 125C LT3922IUFD-1 WPBF LT3922IUFD-1 WTRPBF 39221 28-Lead (4mm 5mm) Plastic QFN 40C to 125C LT3922HUFD-1 WPBF LT3922HUFD-1 WTRPBF 39221 28-Lead (4mm 5mm) Plastic QFN 40C to 150C Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with TRMPBF suffix. **Versions of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These models are designated with a W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for thesemodels. Rev. A 2 For more information www.analog.com ISP SW ISN SW V NC C FB NC SS V OUT ISMON GND