Features and Benefits
- ±2% LED Current Regulation
- ±2% Output Voltage Regulation
- 5000:1 PWM Dimming at 100Hz
- 128:1 Internal PWM Dimming
- Spread-Spectrum Frequency Modulation
- Silent Switcher® Architecture for Low EMI
- Operates in Boost, Buck Mode and Buck-Boost Mode
- 2.8V to 36V Input Voltage Range
- Up to 34V LED String Voltage
- 2A, 40V Internal Switches
- 200kHz to 2MHz with SYNC Function
- Analog or Duty Cycle LED Current Control
- Open/Short LED Protection and Fault Indication
- Thermally Enhanced 28-Pin (4mm × 5mm) QFN
The LT3922 is a monolithic, synchronous, step-up DC/DC converter that utilizes fixed-frequency, peak current control and provides PWM dimming for a string of LEDs. The LED current is programmed by an analog voltage or the duty cycle of pulses at the CTRL pin. The LT3922 will maintain ±2% current regulation through an external sense resistor over a wide range of output voltages.
The switching frequency is programmable from 200kHz to 2MHz by an external resistor at the RT pin or by an external clock applied at the SYNC/SPRD pin. With the optional spread spectrum frequency modulation enabled, the frequency varies from 100% to 125% to reduce EMI. The LT3922 also includes a driver for an external high side PMOS for PWM dimming and an internal PWM signal generator for analog control of PWM dimming when an external signal is not available.
Additional features include an accurate external reference voltage for use with the CTRL and PWM pins, an LED current monitor, an accurate EN/UVLO pin threshold, open-drain fault reporting for open-circuit and short-circuit load conditions, and thermal shutdown.
- Automotive and Industrial Lighting
- Machine Vision
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
Demonstration circuit DC2247A is a synchronous 2MHz boost LED driver featuring the LT®3922. The LT3922 features a low EMI Silent Switcher architecture and an optional spread spectrum frequency modulation (SSFM) that further reduces EMI. It has a 2A/36V internal power switch, but the demo board has been configured to use a 4V to 28V input and thus has input overvoltage lockout set at 28V. It drives a single string of LEDs at 330mA up to 34V when the input voltage is between 7V and 28V.
DC2247A comes with low EMI features including optimized layout, SSFM, and input and output filters. It passes CISPR 25 class 5 conducted and radiated EMI. The LT3922 is protected against both open and short LED conditions and reports these faults. It also includes thermal shutdown.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.
Models for the following parts are available in LTspice:
Press Release (1)
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.