L5991 L5991A is a primary controller with standby current-mode control PWM switching frequency up to 1MHz, low start-up current (<120µA), high-current output drive suitable for power MOSFET (1A), fully latched PWM logic with double pulse suppression, programmable duty cycle 100% and 50%, maximum duty cycle limit, standby function, programmable soft start, primary overcurrent fault detection with re-start delay, PWM UVLO with hysteresis, internal 100ns leading edge blanking of current sense, DIP16 and SO16 package.