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PDF LM3550 Data sheet ( Hoja de datos )
| Número de pieza | LM3550 | |
| Descripción | 5A Flash LED Driver | |
| Fabricantes | National Semiconductor Corporation | |
| Logotipo |  |
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LM3550 PRODUCT BRIEF
May 1, 2009
5A Flash LED Driver with Automatic Vf and ESR Detection
for Mobile Camera Systems
General Description
LM3550 is a low noise, switched capacitor DC/DC converter
designed to operate as a current-limited and adjustable (up
to 5.3V) super-capacitor charger. LM3550 features user se-
lectable super-capacitor charge termination voltages and an
optimal charge termination mode that maximizes flash energy
efficiency by accounting for flash element losses. Additional-
ly, the device provides one adjustable constant-current output
(up to 200mA) and one NFET controller ideal for driving one
or more high current LEDs either in a high power Flash mode
or a low power Torch mode.
The LM3550 can be configured to utilize a proprietary super-
capacitor charging scheme (Optimal Mode), allowing faster
charging times (0 to Target Voltage) and lower current source
power dissipation. Optimal Charge mode adapts to changes
in the flash LEDs forward voltage as well as the super-
capacitor's ESR ensuring that the super-capacitor is charged
to the ideal voltage required to sustain constant current flash
operation.
The LED current and Flash pulse duration of the LM3550 can
be programmed via an I2C compatible interface. The Strobe
pin allows the Flash to be toggled via a Flash enable signal
from a camera module. The EOC pin sinks current when the
output voltage reaches 95% of the final value.
The ALD/TEMP input pin allows either a light sensor to adjust
the flash current level based on the ambient light conditions,
or it allows for over-temperature detection and protection of
the LED during high power operation or high ambient tem-
perature conditions by connecting an NTC thermistor tem-
perature monitoring circuit to the pin.
Notice: This document is not a full datasheet. For more
information regarding this product or to order samples,
please contact your local National Semiconductor sales
office or visit http//www.national.com/support/dtr.html.
Features
■ Up to 5A Flash Current
■ 4 Selectable Super-Capacitor Charge Voltage Levels
(4.5V, 5.0V, 5.3V, Optimized)
■ Flash Optimized Charge Mode for Optimal Efficiency
-33% Faster Charge Time Using Optimal Mode
-49% Less Power Dissipated in Current Source using
Optimal Charge Mode
■ Fast Super-Capacitor Charger with 500 mA Input Current
Limit
■ Adjustable Torch Current (60mA to 200mA)
■ Ambient Light or LED Thermal Sensing with Current
Scaleback
■ End-of-Charge Output (EOC)
■ Dedicated Indicator LED Current Source
■ No Inductor Required
■ Manual Flash Enable via Strobe Pin Input
■ Programmable Flash Pulse Duration, and Torch and Flash
Currents via I2C Compatible Interface
■ True Shutdown (LED Disconnect)
■ Flash Time-Out Protection
■ LED Temperature Protection or Ambient Light Sensing Pin
■ Low Profile 20–Pin LLP Package (3.0 mm × 2.5 mm × 0.8
mm)
Applications
■ Camera Phones
■ Digital Still Camera
■ Voltage Rail Management
© 2009 National Semiconductor Corporation 300594
www.national.com
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| Páginas | Total 2 Páginas | |
| PDF Descargar | [ Datasheet LM3550.PDF ] | |
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