First integrated, multichannel LED drivers to offer high efficiency, LED current consistency, 5000:1 dimming range, and space savings

These devices are the first fully integrated, high-brightness LED drivers that address industry needs for mercury-free, high-contrast lighting in displays. These drivers also provide the accurate and matched constant-current control in multiple LED strings required for automotive and other premium LCD displays, such as in notebook and desktop monitors, LCD TVs and industrial LCD panels. Produced with an environmentally friendly, lead-free technology, these LED drivers also are packaged in the industry's smallest footprint.

The MAX16807-MAX16810 feature a current-mode PWM controller. These LED drivers provide 8 or 16 open-drain, constant-current sinking, parallelable outputs, which are resistor-programmable up to 55mA per channel and rated for 36V continuous operation. The PWM controller delivers up to 1A of load current at the maximum 40V output voltage and high efficiency (up to 92% overall efficiency) using an external MOSFET.

MAX16807/MAX16808* operate either in stand-alone mode or with a microcontroller using a 25Mbps, industry-standard (shift-register-plus-latch-type), 4-wire serial interface. A dedicated dimming input provides fast turn-off and turn-on of all LED channels, thus enabling dimming ratios up to 5000:1. The drivers feature a wide adjustable frequency range (25kHz to 1MHz) that allows design optimization based on trade-offs in efficiency, space (by using miniature inductor and capacitors), and EMI minimization.

Migrating to LEDs Brings Advantages and Poses Challenges

The governmental mandate to remove mercury-based light sources (i.e., fluorescent and CCFL lamps) in motor vehicles will force the automotive industry to replace the existing CCFL-based displays (navigation, infotainment) with white-LED (WLED) backlights. White and RGB LED backlight solutions are already appearing in premium LCD displays, such as notebook and desktop displays. LEDs as light sources offer distinct advantages in these premium displays and in multicolor, adjustable architectural and automotive lighting (exterior and interior) applications. LED benefits include minimized form factor, fast transient performance with precise contrast control, precise color adjustment with a rich gamut, and an environmentally friendly (lead-free), energy-saving technology.

Unique LED Driver Design

1. Eliminates the Need for External Controls

The novel architecture for the MAX16807-MAX16810 drivers eliminates the need for multiple other ICs and discrete power devices. Instead, these new LED drivers integrate switch-mode controller, constant-current multichannel LED regulators with high-voltage MOSFET pass elements and interface circuitry.

2. Reduces Total Solution and Production Costs

Besides the space and cost savings from high integration, the MAX16807-MAX16810 were designed to simplify production and reduce manufacturing cost. These LED drivers use one value of a current-setting resistor for multiple channels. Implemented with a common bandgap reference design, this single resistor ensures LED current accuracy and precise color matching. Necessary high performance is achieved, production time saved, and costs lowered.

3. Makes the Drivers Versatile for Many Applications

Flexible topology, yet highly integrated within the industry-smallest packages, makes these ICs suitable for a full range of LCD display products from 3.5" to 50". Typical applications include automotive displays (e.g., navigation or heads-up display), notebook and desktop monitors, and an LCD TV Backlight Unit (BLU). High-output voltage rating enables the highest number of white or red, green and blue LEDs connected in series in each string. This multistring, multiple-LEDs-per-string topology is attractive in decorative and mood lighting applications in architecture and motor vehicles.

Key Driver Specifications

The MAX16807-MAX16810 combine individual constant-current control of each channel with an accurate bandgap reference for the proper accuracy and channel-to-channel matching. By using the integrated switch-mode controller for boost or in a single-ended, primary-inductance converter (SEPIC) buck-boost topology, the wide input-voltage range can be regulated up to 36V continuous (40V absolute maximum) LED voltage. The device input can be directly biased from 8V to 26.5V and higher with a simple external biasing device. Additional driver features include:

• Output-Enable Pin for PWM Brightness Adjustment (Up to 30kHz)
• Up to 5000:1 Dimming Ratio
• Resistor-Programmable Output Current (3.6mA to 55mA per channel)
• 3% Current Matching Among Outputs
• Adjustable 25kHz to 1MHz Oscillator for Switch-Mode Voltage Preregulator
• Open LED Detection (MAX16808, MAX16810)
• Turn-On/Off of Individual Output Channels with a Serial Bus
• Overtemperature Protection

LED technology development is fast-paced and challenges LED driving electronics. It is imperative that LED drivers provide accurate and matched constant-current control over multiple LED strings. Driver control must operate from a wide-range input supply, optimized for an application, and must span a wide temperature range. These devices operate over the -40°C to +125°C temperature range and are available in a thermally enhanced, 28-pin, exposed pad TSSOP package (MAX16807, MAX16808) and 38-pin, 7mm x 5mm TQFN package (MAX16809, MAX16810). The pricing starts at $2.71 for MAX16809/10 and $2.04 for MAX16807/08 (1000-up, FOB USA). For more information please visit http://www.maxim-ic.com/MAX16807-10info

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