LED driver keeps intensity consistent despite vehicle’s internal fluctuations
Design flexibility is afforded with the ALED6000 single-chip automotive LED driver, says STMicroelectronics. It has an integrated DC/DC converter and is engineered to keep the lighting intensity consistent as electrical conditions within the vehicle fluctuate.
The ALED6000 drives a single string of LEDs at up to 3A and has a wide input voltage range of 4.5 to 61V. It is suitable for exterior lighting such as daytime running lights, headlights, rear lights, stop lights, and turn signals, as well as interior lighting.
The ALED6000 implements digital dimming and has a dedicated pin to apply the PWM control signal. There is also an enable pin and a sync pin that ensures low noise in multi-device applications. The output current is accurate within 3.2 per cent and is monitored with a sense resistor that has a typical voltage drop of 250mV. The quiescent current is just 2.4mA in operation and 11 microA in shutdown. The design also includes a VBIAS auxiliary input pin and pulse skipping operation at light load to ensure high efficiency across the load range.
The on-chip converter allows buck, buck/boost, and floating-boost topologies, which allows it to power LED strings that require a voltage above or below the input voltage while also handling supply fluctuations. The converter can operate in low-dropout mode with close-to 100 per cent duty cycle if the input voltage falls near or below the programmed output.
In the event of over-current, the ALED6000 invokes pulse-by-pulse protection to limit the output current at the preset maximum. There is also programmable soft-start circuitry to limit inrush current, and thermal protection with auto-recovery. Both the output-current limit and converter switching frequency can be selected using external components, allowing the inductor to be optimised for high energy efficiency, fast dynamic response, small size, and low output ripple in conjunction with a low -ESR capacitor.
The AEC-Q100 qualified ALED6000 automotive LED driver is in production now in the HTSSOP16 package. STMicroelectronics also offers the STEVAL-ILL089V1 evaluation kit.
