Smart LED driver produces sophisticated light effects in mobile devices
The AS3668’s lighting effects enhance the appearance and perceived value of a mobile device and act as an additional user interface. Its 12-bit PWM dimming function enables, for instance, a smooth ‘breathlight’ effect with visually seamless transitions between lower and higher brightness levels. The IC also has an audio synchronization mode in which the LED changes brightness and color in response to audio content. The baseband-independent solution provided by the AS3668 means that light patterns – for instance to indicate to the phone or tablet user that they have missed calls or unread text messages, or that an incoming call is waiting – can be continually produced while the baseband stays in its lowest-power ‘deep sleep’ mode.
System power consumption for LED indicator lights driven by the AS3668 is therefore much lower than in conventional implementations using a simple transistor arrangement controlled by the baseband. These conventional designs require the baseband to be activated each time an LED requires input current, and this drains the phone’s battery quickly because the baseband consumes large amounts of power when in active mode.
The AS3668 is a highly efficient charge pump-based programmable LED driver IC. It provides accurate current sources of up to 25 mA for each LED, enabling the generation of a choice of light colors when used with an RGB/W (red, green, blue and white) cluster of LEDs. The device draws just 0.2 mA (typical) in stand-by mode. A programmable VBAT monitor offers fail-safe operation in all system environments, and an automatic start-up pattern can be enabled to indicate to the user that the mobile device is connected to a charger, even if the battery has too little power for the baseband to wake up and start the system.
The IC provides a choice of light patterns, rise and fall timing, pause, pulse-skip, color variations and audio synchronization. Implementation in a target system is facilitated by a simple programming interface; only a few commands are required to program the device. Once in the system, the various functions can be represented in the user interface, and can therefore enable user adjustment of light patterns and colors.
The AS3668 smart LED driver is available in a miniature 1.26mm x 1.68mm 12-pin WL-CSP package.
www.austriamicrosystems.com/LED-driver/AS366
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