Datasheet LT3922-1 (Analog Devices)

LT3922-1 36V, 2.3A Synchronous Step-Up LED Driver with 25,000:1 PWM Dimming
FEATURES DESCRIPTION
n
±2% 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
25,000:1 PWM Dimming at 100Hz
control and provides PWM dimming for a string of LEDs. n
128:1 Internal PWM Dimming
The LED current is programmed by an analog voltage or n
Spread Spectrum Frequency Modulation
the duty cycle of pulses at the CTRL pin. The LT3922-1 n
Silent Switcher
®
Architecture for Low EMI
will maintain ±2% current regulation through an external n
Operates in Boost, Buck Mode and Buck-Boost Mode
sense resistor over a wide range of output voltages. 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 generator for analog control of PWM dimming. When an external signal is available, the LT3922-1 can perform
APPLICATIONS
25,000:1 PWM dimming with 100Hz PWM pulses. n Automotive and Industrial Lighting n Machine Vision Additional features include an accurate external reference voltage for use with the CTRL and PWM pins, an LED All registered trademarks and trademarks are the property of their respective owners. Protected by U.S. patents, including 7199560, 7321203, and other patents pending. current monitor, an accurate EN/UVLO pin threshold, open-drain fault reporting for open-circuit and short-circuit load conditions, and thermal shutdown.
TYPICAL APPLICATION 30V, 333mA Boost LED Driver with 25,000:1 PWM Dimmming
L1, 2.2µH 0.1µF VIN VIN SW BST 8V TO 27V VOUT 4.7µF 1M 0.47µF GND EN/UVLO 0.47µF 365k VOUT OVLO 1M ILED LT3922-1 100mA/DIV 59.0k FB 10µF 33.2k V GND REF 1µF VPWM CTRL ISP 2V/DIV PWM 300mΩ SYNC/SPRD ISN INTVCC 200ns/DIV 100k PWMTG M1 INFINITE PERSISTENCE V 39221 TA01b FAULT ISMON IN = 12V fPWM = 100Hz SS RT RP VC 2.2µF 30V 45.3k 51k 333mA 10nF LED 2MHz 1nF L1: WURTH 74437324022 39221 TA01a M1: VISHAY Si2319CDS Rev 0 Document Feedback For more information www.analog.com 1 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL CHARACTERISTICS TYPICAL PERFORMANCE CHARACTERISTICS PIN FUNCTIONS BLOCK DIAGRAM OPERATION APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION TYPICAL APPLICATION RELATED PARTS