SC4911

Bias/Primary Side PWM Controller with Ultra Low Start-up Current POWER MANAGEMENT Description The SC4911 is a highly integrated bias/primary side PWM controller designed for off-line or isolated dc-dc converters in telecommunication and data communication applications. The high degree of integration minimizes the amount of discrete parts needed and leads to substantial cost and space saving converter designs. The circuitry of the SC4911 includes line voltage UVLO featuring startup current less than 50µA and programwww.DataSheet4U.com mable switching frequency. The device supply is derived from an auxiliary winding on the transformer. The auxiliary winding could also provide output feedback information if an optocoupler is not used. SC4911 Features ‹ ‹ ‹ ‹ ‹ ‹ Programmable switching frequency up to 500kHz Line UVLO Protection Undervoltage Lockout Low startup current (45µA) Cycle by cycle current limit 8 pin MSOP. Available in Lead-free, fully WEEE and RoHS compliant Applications ‹ ‹ ‹ ‹ Telecom isolated converters Offline isolated power supplies Instrumentation power supplies Battery chargers Typical Application Circuit D1 C1 C2 C3 R2 R3 R4 C4 C6 U1 SC4911 Q1 1 8 T1 D2 R1 Vin Vout C5 R5 LUVLO 3 VCC FB OUT 7 4 R7 C7 COMP GND RT ILIM 5 R6 C8 R8 2 R9 Revision: April 5, 2006 6 1 www.semtech.com SC4911 POWER MANAGEMENT Absolute Maximum Ratings Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation o...