Highly-integrated Driver Utilizes Unique Control Method to Equalize Current Between Multiple LED Strings
National Semiconductor Corp. introduced the LM3466, a highly integrated linear LED driver that simplifies the design of high power, wide area lighting fixtures such as streetlights. The LM3466, with just a few passive components, provides a complete system that drives each LED string from any off-the-shelf AC/DC constant-current power supply.
LED drivers today often require multiple components to accurately drive a string of LEDs. In addition, maintaining equal currents among LED strings results in a complex design. National’s LM3466 solves these problems by integrating a MOSFET and utilizing a unique control scheme. The high level of integration enables a basic design of just one LM3466 along with one resistor and one capacitor to drive a string of LEDs. A complete fixture can be constructed by repeating the strings in parallel.
A unique dynamic current equalizing control scheme enables communication between each LM3466 LED driver to divide current equally or ratiometrically amongst multiple active LED strings. No binning of the LEDs is required. During an open (inactive) string state, each LM3466 automatically equalizes current throughout remaining strings to maintain relatively constant output power.
National’s LM3466 linear LED driver integrates a 70V, 1.5A N-Channel MOSFET and features a wide input range of 6V to 70V. LED strings with maximum stack voltages exceeding 70V may be driven with minor changes to the external components. The LM3466 includes a fault status output, input under voltage lockout, current limit and thermal shutdown protection. Linear circuitry wards against any EMI and ensures compliance to the EN 55015 EMC standard or other regional EMC regulatory requirements. Each LM3466 conducts a current up to 1.5A. Communication between the LM3466 and constant current power supply is not required, nor is LED voltage binning. The LM3466 operates with minimal overhead voltage to maximize electrical efficiency. System output power is maintained even for any number of open strings.
Pricing and Availability
Samples are available now with production quantities in July. The LM3466 LED driver is offered in an 8-pin ePSOP package and priced at $1.30 each in quantities of 1,000.
