LM3551 LM3552 led driver schematic circuit design

Posted on Feb 5, 2014

Using the LM3551 and LM3552 are fixed frequency, current mode step-up DC DC converters with two integrated NFETs we can design a very simple and high precision LED brightness control system. The devices are capable of driving loads up to 1A from a single-cell Li-Ion battery. The LM3551 and LM3552 can drive one or more high current flash LEDs eithe

LM3551 LM3552 led driver schematic circuit design
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r in a high power Flash mode or a lower power Torch mode using the TORCH FLASH pin. A programmable Timeout function on the FTO pin forces the internal NFETs to turn off after a certain user defined time. An external SD pin (LM3551) or EN pin (LM3552) is available to put the device into low power shutdown mode. During shutdown, the feedback resistors and the load are disconnected from the input to avoid leakage current paths to ground. The RT value for this LED driver circuit is 17 ohms and the value for the RF is 6. 5 ohms. The output current for IFlash is 250mA and for the ITorch is 75 mA. Some of the features of this LED driver electronic project are : flash timeout protection, independent Torch Flash Shutdown modes, LED disconnect in shutdown, programmable soft-start limits inrush current, over-voltage protection, wide voltage range 2. 7 to 5. 5V, 1. 25MHz constant switching frequency.

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