NS boost converter capable of driving white LED

National Semiconductor Corporation Ns (National Semiconductor Corporation) to launch a suitable for white light emitting diode (LED), the fixed frequency current mode boost DC / DC converter. The LM3557 converter chip provides 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 up to 5 LEDs in series, and provide a 20mA drive current for each of the leds. In addition, because the chip has a 24 volt (V) fixed voltage over-voltage protection function, so no need to add a protective diode chip. The LM3557 chip has a wide range of applications, including color display backlight systems, mobile phones and personal digital assistants (PDA).

Packaging, pricing and availability

National Semiconductor LM3557 chip using 8 pin LLP package, procurement in order to 1000 units, each sold for $0.96, a large number of spot supply.