Serial LED Driver With Current-Regulated, Step-Up DC/DC Converter

The FAN5606 LED Driver generates regulated output cur- rents from a battery with input voltage varying between 2.7V to 5V. An internal NMOS Switch drives an external inductor, and a Schottky Diode delivers the inductors stored energy to the load. Soft start circuitry prevents excessive current drawn from the supply during power on. Any number of LEDs CAN be connected in series as long as the summed forward volt- ages do not lead to exceeding the specied operating output voltage range. In the FAN5606 device, the internal two-bit D/A Converters provide programmability of the output channel current. Analog programming of the output current is also possible in the FAN5606. To do this, ground the B pin and connect a resistor between the A pin and a xed supply voltage. The output current CAN then be programmed to any desired value within its specied range. The Analog version uses a single external resistor to set the current, and to turn the device ON and OFF. The device is available in an 8-lead MLP package. By Fairchild Semiconductor