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HB LED drivers suit car, general lighting apps

Posted: 30 Jan 2008     Print Version  Bookmark and Share

Keywords:HB LED  programmable drivers  EEPROM 


Maxim Integrated Products has introduced the MAX16816, a high-voltage, programmable, high-brightness (HB) LED driver for automotive and general lighting applications. The new device provides many user-programmable features through on-chip non-volatile EEPROM registers. Using an MCU and a single-wire interface, the programming is done either at the factory or by the designer in the field.

The MAX16816 integrates all the building blocks necessary to implement fixed-frequency HB LED drivers with wide-range dimming control. It is configurable to operate as a step-down (buck), step-up (boost) or step-up/down (buck-boost) current regulator. The device also includes an integrated, differential current-sense amplifier and a floating dimming driver capable of driving an n-channel MOSFET.

The MAX16816 is specifically tailored to meet the requirements of the latest front light automotive designs, such as high- and low-beam assemblies, adaptive front light systems, daytime running lights (DRLs) and fog lamps. The device is also suitable for high-power flood lighting, down lighting and projection systems that require high-current LED drive capabilities.

Overcoming traditional design problems
With its advanced programming capabilities, the MAX16816 overcomes many problems and design limitations in older-generation LED drivers. Designers have long struggled to ensure even brightness among LEDs. Typically a customer had to bin LEDs according to brightness level. This was a time-consuming and expensive task. Now, however, the MAX16816's the ability to program LED current eliminates the need for binning LEDs. By allowing LED current adjustment, the MAX16816 compensates for brightness variations during manufacturing.

Traditional LED drivers also offered customers no freedom to select the gate-driver voltage. Designers were thus forced to accept devices with expensive, high-gate-voltage MOSFETs. Now the designer can program the output gate-drive voltage to a value lower than the full-supply voltage. This means that lower cost, low-gate-drive-voltage MOSFETs can be used in the design. It was also not possible then to fine-tune the controller's switching frequency. Because of the MAX16816's programming capabilities, the switching frequency can now be fine-tuned, which helps reduce both system-level noise and EMI.

Software-controlled adjustment of blanking time was also not available. Because the MAX16816 allows the blanking-time value to be programmed into a device, this parameter can now be adjusted easily at the design stage. The capability of adjusting blanking time improves the LED driver's immunity to noise caused by high levels of switching current.

The MAX16816's programmable features include: soft-start, LED current adjust, external MOSFET gate-driver supply voltage, slope compensation, blanking time and enabling/disabling of the internal PWM oscillator. This high level of programmability ensures the design flexibility needed for efficiency, size and minimal EMI.

High power, high voltage benefits
The highly integrated MAX16816 HB LED driver operates from a 5.4V to 76V input voltage range, ensuring cold-start and load-dump (up to 80V) compliance. The driver's high-power capability allows the HB levels to be achieved. The driver enables high-efficiency operation and a wide dimming range (1000:1) with analogue or PWM control. The analogue control signal is compared to an on-board 200Hz ramp and can be used to simplify designs with multilevel brightness adjustment requirements. The LED current control accuracy is ±5 per cent over the entire automotive operating temperature range for excellent brightness matching.

High-voltage capability improves the reliability of the LED lamp/driver combo. The 76V rating of this device allows automotive lighting manufacturers to offer LED lamp systems that are even more reliable than before.

The MAX16816 rugged LED driver also features output overvoltage, overcurrent, overtemperature and LED short protection. The MAX16816ATJ+ is rated for the -40°C to 125°C automotive temperature range. It is available in a Pb-free, 32-pin TQFN package with exposed pad. Prices start at Rs.91.98 ($2.33) (1,000-up, FOB USA).

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