Half of the country can be introduced to drive light-emitting diode boost converter

National Semiconductor Corporation Ns (National Semiconductor Corporation, referred to as the country before the launch of a half) for white light emitting diode (LED), the fixed frequency current mode boost DC/DC converter LM3557. The converter chip can provide a constant current for the LEDs, but a high efficiency external feedback resistor must be used to set the drive current.

The LM3557 chip can drive 5 series light emitting diodes, and can provide 20mA drive current for each led. In addition, because the chip has a 24V fixed voltage over-voltage protection function, so no need to add a protective diode chip. The application of LM3557 chip includes color display backlight system, mobile phone and personal digital assistant (PDA), etc..

The input voltage range of semi LM3557 converter 2.7V to 7.5V; only by adding very small external components; fixed switching frequency is 1.25MHz; with the undervoltage protection function, insufficient input voltage protection function; current limiting cycle; the shutdown mode, there will be no DC grounding line connection the thickness of not more than 1mm; no external compensation.