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WLED flash driver suits handset cameras

Posted: 14 Oct 2009     Print Version  Bookmark and Share

Keywords:WLED  flash driver  converter  handset camera 

MAX8834 driver IC

From Maxim Integrated Products comes the MAX8834, a 1.5A white-LED (WLED) flash driver IC in a tiny, 5mm x 5mm wafer-level package (WLP).

This device integrates an I²C interface, a 5V PWM DC/DC step-up converter, two high-current regulators for movie and flash lighting, and a low-current regulator for driving an indicator LED. Two switching-frequency options allow the designer to optimise for high efficiency (2MHz option, up to 95 per cent at full load) or smallest total solution size (4MHz option, 16.5mm x 16.5mm PCB area). Providing a compact, flexible solution for supporting 5Mpixel cameras, the MAX8834 is suitable for smart phones and other cellular handsets requiring a flash current of 1.5A.

Operating from an input supply as low as 2.5V, the MAX8834 is able to support the next-generation of deep-discharge battery chemistries. The 5V PWM step-up converter integrates an internal switching MOSFET and synchronous rectifier to provide high efficiency and minimum solution size. Two output voltage modes are provided: fixed (3.7V to 5.2V) mode and adaptive mode. In fixed mode, the MAX8834 can be used to drive other loads in the system in addition to the flash LEDs. In adaptive mode, the step-up converter boosts the output voltage only as high as necessary to drive the flash LEDs, providing the best overall efficiency and lowest peak current draw from the input supply. Each of the low-dropout (110mV, max, at 500mA), high-current regulators provides up to 750mA in flash mode and 125mA in movie mode. The low-current regulator provides up to 16mA for driving an indicator LED, and includes programmable ramp-up, ramp-down, and blink timers. All of these features are easily controlled using the I2C interface.

The MAX8834 includes a proprietary, patent-pending MAXFLASH function, which allows the user to program a critical input supply voltage. With MAXFLASH enabled, the MAX8834 will adaptively reduce the flash current when the critical threshold has been reached. This feature is particularly useful for preventing inadvertent system lockup or shutdown if a flash picture is taken when the battery is near the system cut-off voltage. A GSM blank function adaptively lowers the input supply current to a user-programmable level during a PA transmit event, maximising the flash current for any given operating condition.

Other features include an optional remote temperature sensor interface, I²C-programmable safety and watchdog timers, and automatic open/short LED detection. Fault monitors can be read through the I²C interface to facilitate automated factory testing.

The MAX8834 is offered in a 2.5mm x 2mm x 0.65mm, 20-bump WLP, and is fully specified over the -40°C to +85°C extended temperature range. Prices start at 16.50 lakh ($1.65) for 1,000-up, FOB USA. Samples and evaluation kits are available upon request.

Get related application notes and technical articles on Power Design India.





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