LED driver control method eliminates PWM noise

Patented pre-emptive boost (PEB) control is used in the A8060x family of LED backlight drivers. The PEB control eliminates noise that is typically audible.

The A8060x family substantially reduces V out ripple and eliminates the common problem of audible noise from ceramic output capacitors during PWM dimming, says Allegro. It also contributes to designs requiring less output capacitance overall. Systems can achieve an LED brightness contrast ratio of 15,000:1 using PWM-only dimming at 200 Hz. A higher ratio of 150,000:1 is possible when using a combination of PWM and analogue dimming.

The A8060x family offers PMW dimming ratios without analogue adjustment and eliminates noise that is emitted from ceramic capacitors, making them suitable for automotive applications, adds Allegro.

The family consists of the ALT80600 and A80603, which combine a switching converter with integrated MOSFET and four current sinks, and the A80601 and A80602 which drive an external boost FET for higher output power. All devices can be configured in a boost or single-ended primary-inductor converter (SEPIC) topology to cover a range of application configurations. The switching converters are designed for low EMI, including programmable switching frequency, controlled switching slew rate, and programmable dithering. In addition, a clock-out pin allows other switching converters to be synchronised to the A8060x switching frequency for enhanced EMI performance of the overall system.

The A8060x LED backlight drivers are suitable for all types of automotive backlighting, including audio-video systems as well as instrument clusters and heads-up display (HUD). They offer a wide input range from single power supply from 4.5 to 40V and, once started, it can continue to operate down to 3.9V to withstand stop/start, cold crank, double battery and load dump conditions.

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

The devices are all available in a compact 4.0 x 4.0mm QFN-24 wettable flank with exposed thermal pad (ES suffix).


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