SC4905B Datasheet | SEMTECH

Description The SC4905A/B is a 10 pin BICMOS primary side voltage mode controller for use in Isolated DC-DC and off-line switching power supplies. It is a highly integrated solution, requiring few external ponents. The device Features a high speed oscillator with integrated feed forward pensation, accurately programmable maximum duty cycle, voltage mode of operation, line voltage monitoring, supply UVLO, low start up current, low voltage current limit threshold and user accessible reference. .. The SC4905A/B device operates at a fixed frequency, highly desirable for Tele applications. Features a separate SYNC pin which simplifies synchronization to an external clock. Feeding the oscillator of one device to the SYNC of another forces biphase operation (180 degrees apart) which reduces input ripple and filter size. The SC4905A has a turn-on threshold of 4.5V and the SC4905B has a turn-on threshold of about 12 volts. These devices are available in the 10 lead MSOP package. High Performance Voltage Mode PWM Controller PRELIMINARY Features K Operation to 1MHz K Accurate programmable maximum duty cycle K Integrated oscillator/voltage feed forward K K K K K K K K SC4905A/B pensation Line voltage monitoring External frequency synchronization Bi-phase mode of operation for ripple reduction Under 100µA start-up current Accessible reference voltage VDD undervoltage lockout -40°C to 105°C operating temperature 10 lead MSOP package Applications K K K K K Tele equipment and power supplies Networking power supplies Power over LAN applications Industrial power supplies Isolated power supplies Typical Application Circuit Revision 4, April 2002 .semtech. SC4905A/B POWER MANAGEMENT Absolute Maximum Ratings Parameter Supply Voltage Input Voltage (RC, ILIM) Input Voltage (VFF) Input Current (VFF) .. Input Voltage (FB) PRELIMINARY Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters...