Multi-topology converter integrates constant-current PWM

Linear Technology Corp. unveiled a current-mode multi-topology converter with constant-current PWM, dimming for driving high-power LED strings and clusters. According to the company, the LTC3783's proprietary techniques provide extremely fast, true PWM load switching with no transient undervoltage or overvoltage issues. Ratios of 3,000:1 can be achieved digitally as True Color PWM dimming guarantees color integrity of white and RGB LEDs. The LTC3783 allows an additional 100:1 dimming ratio using analog control.

The new controller can be used as a boost, buck, buck-boost, SEPIC or flyback converter, and as a constant-current/constant-voltage regulator. No R_SENSE operation uses the on-resistance of a MOSFET to eliminate the current-sense resistor, increasing efficiency. Target applications for the LTC3783 include high-voltage LED arrays and backlighting, as well as voltage regulators in telecom, automotive and industrial control systems.

The LTC3783 operates from input supplies ranging from 3V to 36V and provides overvoltage protection while regulating output current. Linear Tech added that the integrated drivers for power and load MOSFET switches and the adjustable feedback voltage (0 to 1.23V) make this new product especially convenient for higher-power LED lighting applications. One resistor sets operating frequency from 20kHz to 1MHz. Moreover, to reduce switching noise interference, the LTC3783 is synchronizable to an external clock. Programmable soft-start limits inrush current during startup, preventing input current spikes.

The LTC3783 is rated for operation from -40°C to 85°C with a maximum junction temperature of 125°C. It is offered in 16-lead 5-by-4mm DFN and TSSOP packages. For 1,000-piece orders, pricing starts at $2.85 each.