Programmable linear LED drivers simplify dynamic automotive lighting applications

Diodes Incorporated has introduced the AL58818Q and AL58812Q, a new series of automotive-compliant 18- and 12-channel linear LED drivers designed to supply precise colour mixing and brightness control. These devices are ideal for automotive rear lamp modules, grille and emblem lights, and interior ambient lighting. Beyond lighting, other applications incorporate infotainment displays, automotive status indicator lights, touch panels, and LCDs.

The drivers are designed to simplify the creation of complex and animated LED lighting modules, allowing vivid lighting effects with zero audible noise. Each channel features an internal 12-bit PWM generator operating at 30kHz for fine-tuned colour mixing and brightness control. System designers can select between I2C or SPI digital interfaces through a hardware-selectable pin, delivering improved programming flexibility.

The AL58818Q features 18 channels, making it suitable for up to six RGB LED lighting modules or 18 single-colour LEDs, while the AL58812Q provides 12 channels for up to four RGB LED modules. Each channel delivers up to 70mA of current set by the external resistor. The maximum global 6-bit output current for all channels is adjustable through registers. Each channel also features an internal 30kHz, 12-bit PWM generator for smooth dimming, regardless of the programming registers accessed through the digital interface (I2C or SPI).

The devices feature independent colour-mixing registers and brightness control registers per RGB LED module, allowing over 16 million (256 x 256 x 256) colour combinations. They support logarithmic and linear-scale brightness control for human-eye-friendly visual performance, with a default 12-bit PWM resolution achieved through 9 bits of pure PWM and 3 bits of dithering digital control. The 3-bit dithering scheme improves PWM resolution to 0.0244%. Furthermore, deep dimming is supported, where the internal circuitry converts the PWM signal to analogue dimming when the duty cycle falls below 3%, maintaining overall linearity.

Both devices provide accurate 3% device-to-device and channel-to-channel current matching, ensuring precise colour mixing and uniform colour distribution across various lighting modules and displays. An internal 16MHz oscillator eradicates the need for an external PWM clock, reducing BoM costs. PWM phase-shifting is implemented to delay the activation time of individual LED drivers, thereby greatly decreasing the peak load current from the power supply and reducing input current ripple and audible ringing from ceramic capacitors.

For animation effects like blinking and breathing, the devices deliver LED bank control, allowing channels to be configured for either independent or bank-controlled operation. This simplifies software effort for global LED effects.

The devices each feature an open-drain FAULT indication pin and registers to report issues such as LED open/short circuits, UVLO, pre-UVLO warning, OTP, and pre-OTP warning. Individual fault mask registers permit designers to enable or disable fault reporting for specific channels.

The AL58818Q and AL58812Q support an ultra-low quiescent shutdown current of 1µA. They automatically enter a power-saving mode, consuming a maximum of 15µA, when all LED outputs are inactive for more than 30ms.

Both parts are offered in the W-QFN5050-40/SWP (Type A1) package, featuring wettable flanks to facilitate automated optical inspection and ensure good solderability. Complementing these devices is the previously released 36-channel AL5887Q, which has the same feature set.

Design tools for these devices incorporate the RGB 3-in-1 evaluation board, which features an on-board MCU.