100-V linear LED driver aims to de-clutter low-power lighting designs

July 11, 2012 // By Paul Buckley
Diodes Incorporated has introduced the AL5801 linear LED driver which only needs two additional components to enable designers to simplify automotive interior, signage and general lighting control circuits.

Integrating a 100 V rated N-channel MOSFET with a pre-biased NPN transistor, this small footprint SOT26 packaged device will drive chains of up to 30 low-power, series-connected LEDs with currents from 20 mA to 350 mA.

The AL5801's open-drain output operates between 1.1 V and 100 V, ensuring common 12 V, 24 V and 48 V power rails are supported, while the LED current is set using an external low value resistor. By generating a 0.56 V reference voltage across the resistor, the driver's internal control transistor helps minimize power losses and ensures sufficient supply voltage margin.

Due to the reference voltage's negative temperature coefficient, the output current is automatically reduced at higher temperatures, helping to protect the LED chain from any damage, thus improving overall circuit reliability. In addition, the AL5801's wide operating temperature range of -40 to +150°C means it can be mounted immediately adjacent to LEDs where PCB space is limited.

For applications requiring simple LED dimming, the driver supports PWM output- current regulation, achieved by driving its bias pin with a PWM signal via an external open-collector NPN transistor or open-drain N-channel MOSFET.

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