Product category:
Power Supply ICs and Controllers
News Release from: Linear Technology Corp | Subject: LTC3217
Edited by the Electronicstalk Editorial
Team on 10 March 2006
Charge pump drives multiple high current
LEDs
The LTC3217 is a 850kHz, high efficiency 1x/1.5x/2x multimode charge pump for driving multiple high current LEDs in cellular phone camera applications.
Linear Technology has announced the LTC3217, a 850kHz, high efficiency 1x/1.5x/2x multimode charge pump for driving multiple high current LEDs in cellular phone camera applications Using constant-frequency operation for low noise, it can drive up to four LED current sources at up to 600mA total output current, all from a compact 3 x 3mm QFN package
This article was originally published on Electronicstalk on 28 Jul 2004 at 8.00am (UK)
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Shutdown mode and current output levels are selected via two logic input pins.
The LTC3217's voltage range of 2.9 to 4.5V is optimised for single cell Li-ion inputs.
Efficiencies when driven from a Li-ion battery (3.6V nominal) reach 92%, maximising battery run-time.
It only requires four small capacitors and two resistors to create a tiny, low profile (less than 20mm2, 0.75mm high) solution footprint.
The LTC3217 charge pump automatically optimises efficiency based on input voltage and LED forward voltage conditions.
The device powers up in 1x mode and automatically switches to boost mode (1.5x) when any enabled LED current source approaches dropout; a subsequent dropout switches the part into 2x mode.
High and low LED current levels are programmed via resistors.
Brightness is controlled by selecting each or both current set resistors via the enable inputs.
Brightness can also be controlled by pulsewidth modulation of the EN2 pin.
Internal circuitry prevents inrush current and excessive input noise during startup and mode switching; in addition the device has open/short LED protection.
The LTC3217EUD is available from stock in a 16-lead QFN (3 x 3mm) package.
Pricing starts at $1.70 each for 1000-piece quantities. Request a free brochure from Linear Technology Corp ...
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