YB1522 - Step-up DC-DC Converter White LED Driver
The YB1522 is a step-up DC-DC converter; with wide input voltage range from 3V to 16V, which operates as current source to drive up to 3S7P to 3S10P (VIN at 3V to 5V).
Series connecting of the LEDs provides identical LED currents resulting in uniform brightness and eliminating the need for ballast r