POWER LOSS (W) LTC3541 High Efficiency Buck + VLDO Regulator FEATURES DESCRIPTION n High Efficiency, 500mA Buck Plus 300mA VLDO The LTC 3541 combines a synchronous buck DC/ Regulator DC converter with a very low dropout linear regulator n Auto Start-Up Powers Buck Output Prior (VLDO) to provide up to two output voltages from a single to VLDO/Linear Regulator Output input voltage with minimal external components. When n Independent High Efficiency, 500mA Buck configured for dual output operation, the LTC3541s auto (V : 2.7V to 5.5V) start-up feature will bring the Buck output into regulation IN n 300mA VLDO Regulator with 30mA Standalone Mode in a controlled manner prior to enabling the VLDO regulator n No External Schottky Diodes Required output without the need for external pin control. VLDO/ n Buck Output Voltage Range: 0.8V to 5V linear regulator output prior to Buck output sequencing n VLDO Input Voltage Range (LV ): 0.9V to 5.5V may also be obtained via external pin control. The input IN n VLDO Output Voltage Range VLDO: 0.4V to 4.1V voltage range is ideally suited for Li-Ion battery-powered n Selectable Fixed Frequency, Pulse-Skip Operation or applications, as well as powering sub-3.3V logic from 5V n Burst Mode Operation or 3.3V rails. n Short-Circuit Protected The synchronous buck converter provides a high efficiency n Current Mode Operation for Excellent Line and Load output, typically 90%, capable of providing up to 500mA Transient Response of continuous output current while switching at 2.25MHz, n Constant Frequency Operation: 2.25MHz allowing the use of small surface mount inductors and ca- n Low Dropout Buck Operation: 100% Duty Cycle pacitors. A mode-select pin allows Burst Mode operation n Small, Thermally Enhanced, 10-Lead (3mm 3mm) to be enabled for higher efficiency at light load currents, or DFN Package disabled for lower noise, constant frequency operation. APPLICATIONS The VLDO regulator provides a low noise, low voltage output capable of providing up to 300mA of continuous n PDAs/Palmtop PCs output current using only a 2.2F ceramic capacitor. The n Digital Cameras input supply voltage of the VLDO regulator (LV ) may IN n Cellular Phones come from the buck regulator or a separate supply. n PC Cards L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and VLDO is a n Wireless and DSL Modems trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents, including 5481178, 6611131, 6304066, 6498466, 6580258. n Other Portable Power Systems Buck (Burst) Efficiency and Power Loss vs Load Current TYPICAL APPLICATION 100 1 LTC3541 Typical Application 90 V IN EFFICIENCY 2.9V TO 5.5V 80 10F 0.1 V IN 70 ENVLDO ENBUCK 60 2.2H V OUT2 POWER LOSS SW LV 1.5V 50 0.01 OUT V OUT1 300mA 2.5V LV 412k 40 IN LTC3541 200mA 22pF 243k 30 LFB 0.001 2.2F 10F 20 BUCKFB MODE V = 3.3V 10 IN 115k 150k PGND GND V = 2.5V OUT 0 0.0001 1 10 100 1000 3541 TA01a LOAD CURRENT (mA) 3541 TA01b 3541fb 1 FFoorr mmoorree iinnffoorrmmaattiioonn wwwwww..lliinneeaarr..ccoomm//LLTTCC33554411 EFFICIENCY (%)LTC3541 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Supply Voltages: TOP VIEW V , LV .................................................. 0.3V to 6V IN IN V 1 10 SW LV V ..........................................................<0.3V IN IN IN ENBUCK 2 9 ENVLDO Pin Voltages: 11 BUCKFB 3 8 MODE ENVLDO, ENBUCK, MODE, SW, LFB 4 7 GND LFB, BUCKFB ............................ 0.3V to (V + 0.3V) LV 5 6 LV IN OUT IN Linear Regulator I (100ms) (Note 9) ......100mA OUT(MAX) DD PACKAGE Operating Ambient Temperature Range 10-LEAD (3mm 3mm) PLASTIC DFN T = 125C, = 43C/W (Note 2) ....................................................40C to 85C JMAX JA EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB Junction Temperature (Note 5) ............................. 125C Storage Temperature Range .................. 65C to 125C