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LED flash driver packs ultrathin supercapacitor

Posted: 29 Jun 2009     Print Version  Bookmark and Share

Keywords:LED  flash driver  phones camera  photo flash light 

NCP5680 flash driver

ON Semiconductor has released the NCP5680 supercapacitor-optimised LED flash driver capable of delivering up to 10A for photo flash and video light in ultraslim camera phones and compact digital cameras.

"The NCP5680, combined with an ultrathin prismatic supercapacitor, delivers an ideal LED flash and power management solution for slim camera phones and digital cameras," said Marie-Therese Capron, ON Semiconductor director of low voltage power management products. "This total LED flash solution supplies comparable light energy to xenon flash, but with only half of the comparable solution height and no need for an extra LED for video capture. The NCP5680 enables the Li-ion battery to support more power-hungry functions for a longer time."

When combined with the latest thin, prismatic supercapacitors (such as those offered by CAP-XX and licensed by Murata Manufacturing Co. Ltd Japan with a capacitance of up to 0.9F at 5.5V and the high-power LED OSLUX from Osram), NCP5680 complements the Li-ion battery by supplying high-peak-current of up to 10A for flash lighting optimised for use with the BriteFlash Power Architecture developed by CAP-XX. Fully programmable control of charging and discharging of the supercapacitor and unique overload protection ensure the right amount of light is provided for high-quality photography. The integrated driver can also power other high-peak-current circuits in portable systems, such as audio amplifiers, extending the useful battery operating time.

Low-light conditions
To produce high-resolution pictures in low-light conditions, cameras of 5Mpixels or more require a high-intensity flash. Today's white LEDs can deliver this level of light energy, but require up to 400 per cent more power than a camera battery can provide. To support the battery, the NCP5680 manages a supercapacitor to drive the LED flash to full intensity, supplying high-peak-current up to 10A. The integrated driver in the NCP5680 also manages the supercapacitor to handle other peak-power needs: zoom, auto-focus, audio, video, wireless transmissions, GPS readings and RF amplification.

The NCP5680 integrates all circuitry required to charge the supercapacitor, manage in-rush current and control LED current, thus saving designers development time, board space and component cost. Fully programmable control of charging and discharging of the supercapacitor ensures the right amount of light for high-quality photography.

The I²C registers in the NCP5680 allow users to adjust the output current and flash duration of each of the two LEDs in real time. Hence, this solution can perform different lighting effects such as indicator light, pre-flash and power flashlight for photographing and torchlight for video recording. When connecting to an ambient light sensor, the NCP5680 will automatically limit the flash duration to prevent photo over-exposure, thus preserving the photo quality. Additionally, the supercapacitor charging current is adjustable through an I²C register. NCP5680 can disable the charging operation during global system for mobile (GSM) transmission to limit the current drawn from the battery.

The NCP5680 has multiple built-in protection mechanisms, including flash time out, temperature detection, overload protection and short circuit protection. The device protects the flash circuitry from any faulty conditions of the driving circuit, as well as for the LED.

Available in the 3.5mm x 3.5mm x 0.55mmµQFN-24 package, the NCP5680 is priced at Rs.53.89 ($1.10) per unit in 3,000-unit quantities.

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