30 June 2009
LED flash driver maximises limited currents
A dual white led flash driver, designed to maximise the limited current available in battery operated digital cameras, is said to increase flash brightness to over 200 lumens.
According to Analog Devices, its ADP 1655 inductor based flash driver can improve the reliability of high resolution camera operation in hand held devices. In cell phone applications the company says that the driver's proprietary transmit masking function allows the camera flash to run at a higher led current, while simultaneously operating the phone's rf transceiver to monitor the cellular base station for incoming signals.
The ADP1655 integrates a 2MHz synchronous boost converter, a 500mA programmable current source and an I2C, which enables timers and currents to be programmed and data to be read back relative to system operation and safety controls. It has been designed to improve flash brightness by allowing the camera to increase current to the led without crossing safety thresholds that could trigger the phone to shut down.
The new driver also includes a high side current source that allows the flash led string to be connected to the camera's ground plane. This, says ADI, eliminates the need to route the leds back to the IC and allows designers to simplify printed circuit board routing. This, in turn reduces circuit trace length and thermal dissipation and allows the camera to be designed using a more compact layout.
Power management
Author
Chris Shaw
Supporting Information
Websites
http://www.analog.com
Companies
Analog Devices
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