Cell Phone Camera LED Driver provides 92% efficiency.
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Press Release Summary:
Housed in 3 x 3 mm QFN package, 850 kHz Model LTC3217 drives up to 4 LED current sources at up to 600 mA total output current. Multimode, automatic switching 1x/1.5x/2x charge pump features input voltage range of 2.9-4.5 V, making it suited for single cell Li-Ion inputs. Unit optimizes efficiency based on VIN and LED forward voltage conditions. Brightness can be controlled by selecting each or both current set resistors via enable inputs, as well as by PWM of EN2 pin.
Original Press Release:
600mA Cell Phone Camera LED Driver Features Low Noise and 92% Efficiency
MILPITAS, CA - December 21, 2005 - Linear Technology Corporation announces the LTC3217, a 850kHz, high efficiency 1x/1.5x/2x multimode charge pump for driving multiple high current LEDs in cellular phone camera applications. Utilizing constant-frequency operation for low noise, it can drive up to 4 LED current sources at up to 600mA total output current, all from a compact 3mm x 3mm QFN package. Shutdown mode and current output levels are selected via two logic input pins. The LTC3217's voltage range of 2.9V to 4.5V is optimized for single cell Li-Ion inputs. Efficiencies when driven from a Li-Ion battery (3.6V nominal) reach 92%, maximizing battery run-time. It only requires four small capacitors and two resistors to create a tiny, low profile (<20mm2, 0.75mm high) solution footprint.
The LTC3217 charge pump automatically optimizes efficiency based on VIN 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 pulse width modulation of the EN2 pin. Internal circuitry prevents inrush current and excessive input noise during start-up and mode switching; in addition the device has open/short LED protection.
The LTC3217EUD is available from stock in a 16-lead QFN (3mm x 3mm) package. Pricing starts at $1.70 each for 1,000-piece quantities.
Summary of Features: LTC3217
Up to 92% Efficiency without Inductors
Multimode, Automatic Switching 1x/1.5x/2x Charge Pump for Optimal Efficiency
Up to 600mA Total Output Current
4 Low-Dropout Current Sources Available as High Current Camera LED Drivers
PWM Brightness Control via the EN2 Pin
Low Noise, Constant Frequency Operation
Internal Soft-Start Limits Inrush Current During Start-Up and Mode Switching
Open/Short LED Protection
2.9V to 4.5V Input Voltage Range
3mm x 3mm x 0.75mm QFN-16 Package
Company Background
Linear Technology Corporation, a manufacturer of high performance linear integrated circuits, was founded in 1981, became a public company in 1986 and joined the S&P 500 index of major public companies in 2000. Linear Technology products include high performance amplifiers, comparators, voltage references, monolithic filters, linear regulators, DC-DC converters, battery chargers, data converters, communications interface circuits, RF signal conditioning circuits, and many other analog functions. Applications for Linear Technology's high performance circuits include telecommunications, cellular telephones, networking products such as optical switches, notebook and desktop computers, computer peripherals, video/multimedia, industrial instrumentation, security monitoring devices, high-end consumer products such as digital cameras and MP3 players, complex medical devices, automotive electronics, factory automation, process control, and military and space systems. For more information, visit www.linear.com.
LT and LTC are registered trademarks of Linear Technology Corp.
North America and General Information
John Hamburger
Tel: (408) 432-1900 ext. 2419
jhamburger@linear.com
Doug Dickinson
Tel: (408) 432 1900 ext. 2233
ddickinson@linear.com
