2-terminal constant-current linear regulator improves LED current tolerance

December 08, 2014 // By Graham Prophet
Diodes Inc’s AL5809 is a two-terminal PowerDI-123 packaged device that you use instead of a current-limiting resistor or a more complex current feed built from discrete parts; it provides an improved accuracy, cost-effective solution for constant-current linear driving of LEDs.

With 1.2W maximum power dissipation, 20 ppm/°C temperature stability and high power-supply rejection ratio, the AL5809 delivers LED currents with a ±5% tolerance over a wide temperature range, greatly simplifying the solutions for its target applications of LED signage, LED strip lighting and low-current retrofit lamps. The AL5809 is a small footprint, low BOM-cost LED driver that is simple to use and provides improved accuracy and all-round higher performance than competitive alternatives or discrete circuit designs.

The AL5809 is specified for the -40°C to +125°C temperature range, with an operating voltage (between the two terminals) from 2.5V to 60V and is offered in various fixed-output current versions; this removes the need for external current setting resistors. The PowerDI-123 package fixed-output current options are 15, 20, 30, 40, 50, 60, 90, 120 and 150 mA, while in the alternative SOD-123 package there are current output versions of 15, 20, 30, 40 and 50 mA.

As well as meeting the needs of designs requiring a simple linear regulator (e.g., no inductor or external resistor), the AL5809 provides additional performance features; over-temperature protection (OTP) and the ability to drive both low- and high-side LED chains.

The part costs $0.10 for the SOD-123 packaged devices, $0.11 for the 15-50mA parts in the PowerDI-123 package, and $0.12 for the higher current 60-150mA PowerDI-123 packaged devices (all at 10,000).

Diodes; www.diodes.com