LT1432 Datasheet | Linear Technology

LT1432 5V High Efficiency Step-Down Switching Regulator Controller Features s s s s s s s s DESCRIPTIO Accurate Preset +5V Output Up to 90% Efficiency Optional Burst Mode for Light Loads Can be Used with Many LTC Switching ICs Accurate Ultra-Low-Loss Current Limit Operates with Inputs from 6V to 30V Shutdown Mode Draws Only 15µA Uses Small 50µH Inductor The LT1432 is a control chip designed to operate with the LT1170/LT1270 family of switching regulators to make a very high efficiency 5V step-down (buck) switching regulator. A minimum of external ponents is needed. Included is an accurate current limit which uses only 60m V sense voltage and uses “free” PC board trace material for the sense resistor. Logic controlled electronic shutdown mode draws only 15µA battery current. The switching regulator operates down to 6V input. The LT1432 has a logic controlled “burst” mode to achieve high efficiency at very light load currents (0 to 100m A) such as memory keep-alive. In normal switching mode, the standby power loss is about 60m W, limiting efficiency at light loads. In burst mode, standby loss is reduced to approximately 15m W. Output current in this mode is typically in the 5m A to 100m A range. The LT1432 is available in 8-pin surface mount and DIP packages. The LT1170/LT1270 family will also be available in a surface mount version of the 5-pin TO-220 package. For 3.3V versions contact Linear Technology Corporation. APPLICATI s s s s Laptop and Palmtop puters Portable Data-Gathering Instruments DC Bus Distribution Systems Battery-Powered Digital Widgets TYPICAL APPLICATI + VSW C1 330µF 35V C6 0.02µF R1 680Ω C4 0.1µF D1 MBR330p C5 0.03µF FB VC LT1170 LT1271 10µH 3A 100µF 16V + D2 1N4148 OPTIONAL OUTPUT FILTER L1 50µH R2- 0.013Ω + VC VIN LT1432 DIODE V+ VLIM VOUT GND × C2 390µF 16V VOUT 5V 3A- - EFFICIENCY (%) C3 4.7µF TANT + MODE LOGIC 220p F <0.3V = NORMAL MODE >2.5V = SHUTDOWN OPEN = BURST MODE MODE - R2 IS MADE FROM PC BOARD...