Linear Technology Corporation has introduced the LT3591, a high efficiency, constant current white LED driver in a 2mm x 3mm DFN package. The device integrates Schottky diodes on-chip, eliminating the extra cost and space required for external diodes. The unique high-side LED current-sense topology allows the LED cathode to be directly grounded, creating a single-wire current source.
The LT3591 drives up to 10 white LEDs with a single-cell Li-Ion battery at over 78% efficiency. It switches at 1MHz, allowing the use of tiny inductors and capacitors while keeping switching noise out of critical RF bands. The LT3591 combines high efficiency, low noise and minimal overall solution footprint, making it ideal for handheld applications that require up to 10 white LEDs for backlighting.
The LT3591 operates in a constant current source mode to ensure consistent LED brightness. The LED forward voltage drop varies with temperature, manufacturing tolerance, and ageing, but regardless of how the LED's forward voltage drop changes, the LT3591 provides the same amount of current for each white LED. The device's True Color PWMTM dimming has a wide dimming range of up to 80:1. Other features include output voltage limit when the LED is disconnected and ±5% reference accuracy.
The LT3591 is available from stock in an 8-lead 2mm x 3mm DFN package. Buy in 1,000-piece quantities starting at $1.40 each.
LT3591 performance summary:
Drive up to 10 white LEDs from a 3V power supply
High-voltage side detection allows "single line current source"
Internal Schottky diode
Single pin dimming and shutdown
80:1 True Color PWM dimming range
42V LED open circuit protection
1MHz switching frequency
±5% benchmark accuracy
VIN range: 2.5V to 12V
Flat 8-lead DFN package (3mm x 2mm x 0.75mm)
Source: Electronic Engineering
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