Micrel MIC3287 PWM White LED Drivers
Micrel's MIC3287 PWM White LED Drivers are a 1.2MHz pulse-width modulated (PWM) step-up switching regulator that is optimized for constant current white LED driving applications. With a maximum output voltage of 24V and a switch current of over 350mA, the MIC3287 drives a string of up to four white LEDs in series, ensuring uniform brightness and eliminating several ballast resistors. The MIC3287 implements a constant frequency 1.2MHz PWM current-mode control scheme. The high frequency PWM operation saves board space by reducing external component sizes. The added benefit of the constant frequency PWM control scheme as opposed to variable frequency control schemes is much lower noise and input ripple injected back to the battery source. To optimize efficiency, the feedback voltage is set to only 250mV. The MIC3287 is also available with a maximum 24V over voltage protection.