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HB LED driver maximises system flexibility

Posted: 24 Oct 2008     Print Version  Bookmark and Share

Keywords:LED driver  four-string  green lighting technology  LED current 

Maxim Integrated Products has announced the MAX16826 programmable, four-string high-brightness (HB) LED driver for white, RGB, and RGB-plus-amber LED configurations. Designed to enable the transition to green lighting technology in automotive applications, this device maximises system flexibility and provides the lowest solution cost for backlight drivers.

The MAX16826 integrates a switching regulator controller; a 4-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, thereby reducing implementation cost.

Offering an unparalleled combination of configurability and performance, the MAX16826 is ideal for backlighting automotive infotainment displays, automotive display clusters, industrial and desktop monitors, and LCD TVs. It is also well suited for adaptive front lights and low-/high-beam assemblies, as well as other solid-state lighting (SSL) applications.

Specifically designed for automotive applications, the MAX16826 provides OEMs with a highly cost-efficient, scalable solution. The device's advanced 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 innovative 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 and greatly simplifies production. 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.

The MAX16826 drives external MOSFETs for both the switching converter and LED current regulators allowing the device to drive more HB LEDs per string and more LED current across each string. This enables 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.

For enhanced flexibility, the switching regulator can be 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. Additionally, each current sink features a direct-PWM input to enable independent LED-dimming control for each channel. Thus, designers can independently adjust the LED brightness for each colour in RGB applications for optimum colour control.

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 -40°C to +125°C automotive temperature range. The device can withstand load-dump transients up to 40V, and can operate under cold-crank conditions.

The MAX16826 is available in a thermally enhanced, 5mm x 5mm, 32-pin TQFN package. Prices start at Rs.88.17 ($2.05) (1000-up, FOB USA).

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