ST778

www.DataSheet4U.com ST777/778/779 LOW VOLTAGE INPUT, 3-3.3V/5V/ADJUSTABLE OUTPUT DC-DC CONVERTER WITH SYNCHRONOUS RECTIFIER s s s s s s s s s 1V TO 6V INPUT GUARANTEES START-UP UNDER LOAD MAXIMUM OUTPUT CURRENT OF 300mA (778 OR 779 ADJUSTED TO 3V) LOAD FULLY DISCONNECTED IN SHUTDOWN TYPICAL EFFICIENCY OF 82% INTERNAL 1A POWER SWITCH AND SYNCHRONOUS RECTIFIER ADJUSTABLE CURRENT LIMIT ALLOWS LOW-COST INDUCTORS SUPPLY CURRENT OF 270µA (NO LOAD) SHUTDOWN SUPPLY CURRENT 20µA PACKAGE AVAILABLE: DIP-8 AND SO-8 DIP-8 SO-8 DESCRIPTION The ST777/778/779 are dc-dc converters that step-up from low voltage inputs requiring only three external components, an inductor (typically 22µH) and two capacitors. The device include a Sinchronous Rectifier that eliminates the need for an external catch diode, and allows regulation even when the input is greater than the output. SCHEMATIC DIAGRAM VIN 100µF Unlike others step-up DC-DC converters the ST777/778/779’s Sinchronous Rectifier turns off in the shutdown mode, fully disconnecting the output from the source. This eliminates the current drain associated with conventional step-up converters when off or in shutdown. Supply current is 270µA under no load and only 20µA in stand by mode. 22µH RLIM 2 IN DELAY TIMER 1 5 ILIM LX ACTIVE RECTIFIER tOFF SWITCH DRIVER DELAY TIMER OUT 6 VO 100µF tON 1 : N RECTIFIER CONTROL PGND 4 SEL 8 VREF 1.25V 7 SHDN SHUTDOWN CONTROL AGND 3 October 2002 1/11 ST777/778/779 ABSOLUTE MAXIMUM RAT...