AEC-Q100 4.5V to 40V LED Backlight Drivers Eliminate Audio Noise

Allegro MicroSystems announced the A8060x family, its latest generation of advanced LED backlight drivers. The device family is designed with a patented Pre-Emptive Boost (PEB) control, which eliminates noise that is typically audible.

The A8060x device family is suitable for all types of automotive backlighting, including audio-video systems and heads up display (HUD) as well as instrument clusters.

The company says that the PEB control in the A8060x family substantially reduces Vout ripple and eliminates the typical problem of audible noise from ceramic output capacitors during PWM dimming, while also needing less output capacitance overall.

Allegro says that with the A8060x family of LED backlight drivers, systems can achieve an LED brightness contrast ratio of 15,000:1 using PWM-only dimming at 200Hz. When using a combination of PWM and analog dimming, a higher ratio of 150,000:1 is possible.

"This family of LED drivers alleviates significant customer pain points in the areas of audible noise and device footprint," explains Mark Gaboriault, Allegro's Marketing Director for DC-DC Regulators and LED Drivers. "The A8060x family offers excellent PMW dimming ratios without analog adjustment and eliminates noise that is emitted from ceramic capacitors, making them perfect for automotive applications."

Both the ALT80600 and A80603 combine a switching converter with integrated MOSFET and four current sinks, while the A80601 and A80602 drive an external boost FET for higher output power.

All of the backlight drivers can be configured in a boost or single-ended primary-inductor converter (SEPIC) topology to cover a wide range of application configurations.

Allegro designed the converters for low EMI, including programmable switching frequency and dithering and controlled switching slew rate. In addition, a clock-out pin allows the synchronization of other switching converters to the A8060x switching frequency for enhanced EMI performance of the overall system.

These devices offer a wide input range from single power supply from 4.5V to 40V. Once started, it can continue to operate down to 3.9V. This allows the parts to withstand stop/start, cold crank, double-battery and load dump conditions found in automotive systems.

The robust A8060x has a host of safety and protection features required for automotive applications. The ALT80600 and A80603 feature four LED strings, each capable of up to 120mA with a total LED current of up to 480mA. The A80601 and A80602 provide a total LED current of up to 840mA, via 4 or 6 strings respectively.

These devices are all available in a compact 4x4 QFN-24 wettable flank packages with exposed thermal pad (ES suffix) and have a smaller package than their direct competition.

Switching frequency can either be above or below the AM band. Programmable dithering provides an additional EMI reduction. A synchronization pin allows the external synchronization of switching frequency between 200kHz and 2.3MHz. A ‘Clock-Out' pin lets other converters be synchronized to the ALT80600's switching frequency.

The ALT80600 protects against output short, over temperature, over-voltage, open or shorted diode, or open or shorted LED pin. A cycle-by-cycle current limit guards the internal boost switch against high current overloads. An external P-MOSFET can optionally be used to disconnect input supply in case of output to the ground-short fault.

Features of ALT80600, A80601, A80602, and A80603

• Automotive AEC-Q100 qualified
• Input voltage range of 4.5V to 40V for start/stop, cold crank, and load dump requirements
• Fully integrated LED current sinks and boost converter with internal power MOSFET
• Operate in Boost or SEPIC mode for flexible output
• Programmable boost switching frequency or sync externally from 200 kHz to 2.3MHz
• Clock-Out feature for internal switching frequency
• Adjustable boost frequency dithering to reduce EMI
• Advanced control allows minimum PWM on-time down to 0.3μs, and avoids MLCC audible noises
• LED contrast ratio: 15,000:1 at 200Hz using PWM dimming alone, 150,000:1 when combining PWM and analog dimming
• Excellent input voltage transient response even at lowest PWM duty cycle
• Gate driver for optional PMOS input disconnect switch
• Extensive protection against:
• Shorted boost switch, inductor or output capacitor
• Shorted FSET or ISET resistor
• Open or shorted LED pins and LED strings
• Open boost Schottky diode
• Over-temperature

ALT80600 Only

• Drives up to 11 series white LED in 4 parallel strings, at up to 120mA per string (VF=3.3V max).

A80601

• Enhanced fault handling for ASIL-B system compliance
• Gate driver for external NMOS to deliver higher output power
• Four integrated LED current sinks, up to 210mA each

A80602

• Enhanced fault handling for ASIL-B system compliance
• Gate driver for external NMOS to deliver higher output power
• Six integrated LED current sinks, up to 140mA each

A80603

• Enhanced fault handling for ASIL-B system compliance
• Drives up to 11 series white LED in 4 parallel strings, at up to 120mA per string (VF = 3.3V max).