Maxim develops programmable LED driver

Maxim Integrated Products has introduced the Max16826 programmable, four-string, high-brightness (HB) LED driver for white, RGB and RGB-plus-amber LED configurations.

The Max16826 integrates a switching regulator controller; a four-channel, linear current-source driver; an ADC; and an I2C interface.

The I2C interface allows dynamic programming of the output voltage to maximise power efficiency.

It also allows manufacturers to program LED current for each string to accommodate LED binning variations.

Offering a combination of configurability and performance, the Max16826 is suitable for backlighting automotive infotainment displays, automotive display clusters, industrial and desktop monitors, and LCD TVs.

It is also suited to adaptive front lights and low-/high-beam assemblies, as well as other solid-state lighting (SSL) applications.

With the traction of green initiatives among consumers, OEMs are shifting from CCFLs to HB LEDs for automotive backlighting applications.

HB LEDs consume less power, and they do not contain hazardous materials such as the mercury in CCFLs.

Moreover, consumers benefit from the enhanced colour reproduction and longer lifespans of HB LEDs.

Maxim said that the Max16826 provides OEMs with a cost-efficient, scalable solution.

The device's programming features allow it to be used for multiple designs with minimal component changes.

They also enable system manufacturers to accommodate LED binning variations, thereby reducing overall manufacturing cost.

The Max16826 employs an architecture that allows dynamic programming of the switching regulator's output voltage and the LED current amplitude in each channel.

An internal ADC measures the drain voltage of each HB LED string.

It then makes the measurements available to an external microcontroller through an I2C interface for output-voltage optimisation and LED fault monitoring.

Dynamic programmability allows the same driver circuit to be used for multiple projects by simply adjusting the LED current or voltage through the I2C interface.

This capability eliminates the need for component changes.

Moreover, output-voltage optimisation maximises conversion efficiency by reducing the voltage drop across the linear drivers.

Consequently, it also reduces power dissipation and heat in the display.

Whereas existing designs employ integrated MOSFETs for LED current regulation, the Max16826 drives external MOSFETs for both the switching converter and LED current regulators.

This approach allows the device to drive more HB LEDs per string and more LED current across each string, thus enabling designers to utilise the Max16826 for multiple projects.

It also improves thermal management, because heat is dissipated by more components, and over a larger board area.

The Max16826 is able to detect and react to LED open- and short-circuit faults.

Whenever a fault is detected, the IC triggers internal circuits, which immediately disable the faulty elements.

This integrated fault monitoring protects the HB LED driver and the automotive electrical system from damage.

In addition, the automotive electrical system can read the fault condition through the device's I2C interface, and react accordingly.

The switching regulator can be also configured as a boost or SEPIC converter; the voltage across the driven LEDs can therefore be both higher and lower than the supplied input voltage.

The Max16826 also offers a programmable switching frequency (100kHz to 1MHz) to reduce electromagnetic interference (EMI) in noise-sensitive applications such as automotive displays.

Each current sink features a direct-PWM input to enable independent LED-dimming control for each channel.

Designers can independently adjust the LED brightness for each colour in RGB applications.

Additional features include cycle-by-cycle current limiting, output over-voltage protection, and over-temperature protection.

Designed for harsh operating environments, the Max16826 is fully specified over the -40C to +125C automotive temperature range.

The device can withstand load-dump transients up to 40V, and can operate under cold-crank conditions.

It is available in a thermally enhanced, 5 x 5mm, 32-pin TQFN package.

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