Tiny Package, Low Dropout Current Source

The RT9300A/B low-dropout bias supply for white LEDs is a high-performance alternative to the simple ballast resistors used in conventional white LED designs. The RT9300A/B uses an internal resistor to set the bias current for four LEDs, which are matched to 5%. The RT9300A/B's advantages over ballast resistors include much lower bias variation with supply voltage variation, significantly lower dropout voltage, and in some applications, significantly improved efficiency. The RT9300A/B requires only a 60/45mV dropout voltage at a 20/15mA load on each output to match the LED brightness.