Product category:
Power Supply ICs and Controllers
News Release from: Semtech | Subject: SC4505
Edited by the Electronicstalk Editorial
Team on 14 March 2006
Convertor chip drives handset backlight
and flash
An integrated boost (step-up) DC/DC convertor drives white LEDs in LCD backlight and camera flash applications in cellphones and PDAs.
Semtech Corp has announced the SC4505, an integrated boost (step-up) DC/DC convertor for driving white LEDs in LCD backlight and camera flash applications in cellphones and PDAs The SC4505 features a 2A power switch with an adjustable output voltage of up to 28V to drive two strings of up to six LEDs per string using a single inductor
This article was originally published on Electronicstalk on 16 Jul 2001 at 8.00am (UK)
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Each string features an independent user-selectable current source with the backlight string supporting up to 75mA and the flash string supporting up to 125mA.
The high power level can accommodate high-current LEDs for brighter displays.
The device supports independent control of the backlight and flash functions through separate pins.
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Backlight dimming can be achieved through digital PWM control signals with a range of 50Hz to 50kHz, which maintain peak LED current for maximum brightness.
The camera flash string features a user-controllable flash timeout that reduces LED burn out.
In addition, the flash can be set to 20% of maximum flash current (torch or spotlight mode) for continuous LED lighting.
The convertor operates at a nominal switching frequency of 1MHz with an input range of 2.6 to 16V.
Driving the LEDs in series results in excellent current matching for uniform lighting.
The SC4505's high operating frequency and higher integration reduces board space and BOM costs of the display/flash subsystem.
The SC4505 uses a regulation technique that optimises its operation to seek the highest efficiency irrespective of load current in each string.
This innovative power regulation technology adapts to the instantaneous power requirements of the system, reducing power dissipation while maintaining high efficiency.
"The single inductor design of the SC4505 enables a highly compact and lower cost backlight display and camera flash subsystem for next generation smart phones", said Ven Shan, Vice President of Marketing for Semtech's Power Management Products.
"As handsets become portals for new video and imaging content, the SC4505 will allow smart phone system designers to develop sharper and brighter displays without sacrificing battery life".
The SC4505 can be used to drive up to 12 LEDs which makes it very flexible and suitable for driving backlight displays in devices such as PDAs, GPS devices, portable media players, and portable gaming consoles with 5 to 7in LCDs.
It comes in a 3 x 3mm, 16-pin MLPQ package that is lead free and RoHS/WEEE compliant.
The SC4505 is available immediately in production quantities and is priced at $1.56 each in 1000-piece lots.
Ordering code is SC4505MLTRT.
Semtech offers comprehensive design assistance, including field- and factory-based support.
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