The NCP1561 Push-Pull PWM controller contains all the features and flexibility needed to implement high efficiency dc-dc converters using voltage or current-mode control. This device can be configured in any dual ended topology such as push-pull or half-bridge. It can also be used for forward topologies requiring a 50% maximum duty cycle. This device is ideally suited for 48 V telecom, 42 V automotive systems and 12 V input applications. The NCP1561 cost effectively reduce system part count by incorporating a high voltage startup regulator, line undervoltage detector, single resistor oscillator setting, dual mode overcurrent protection, soft-start and single resistor feedforward ramp generator. The oscillator frequency can be adjusted up to 250 kHz.