POWER LOSS (mW) LTC3548-2 Dual Synchronous, Fixed /Adjustable Output, 2.25MHz Step-Down DC/DC Regulator FEATURES DESCRIPTION n High Ef ciency: Up to 95% The LTC 3548-2 is a dual, constant-frequency, synchro- n 1.8V/800mA Fixed Output and 400mA Adjustable nous step-down DC/DC converter. Intended for low power Output Voltage applications, it operates from 2.5V to 5.5V input voltage n Only 40A Quiescent Current (Both Channels) range and has a constant 2.25MHz switching frequency, n 2.25MHz Constant-Frequency Operation allowing the use of tiny, low cost capacitors and inductors n High Switch Current Limits: 1.2A and 0.7A with a pro le 1.2mm. For channel 1, the output voltage is n No Schottky Diodes Required xed at 1.8V/800mA for channel 2, the output voltage is n Low R Internal Switches: 0.35 adjustable from 0.6V to V Internal synchronous 0.35, DS(ON) IN n Current Mode Operation for Excellent Line 1.2A/0.7A power switches provide high ef ciency without and Load Transient Response the need for external Schottky diodes. n Short-Circuit Protected A user selectable mode input is provided to allow the n Low Dropout Operation: 100% Duty Cycle user to trade-off noise ripple for low power ef ciency. n Ultralow Shutdown Current: I < 1A Q Burst Mode operation provides high ef ciency at light n Power-On Reset Output loads, while pulse-skipping mode provides low noise n Externally Synchronizable Oscillator ripple at light loads. n Small, Thermally Enhanced 3mm 3mm DFN Package To further maximize battery run time, the P-channel APPLICATIONS MOSFETs are turned on continuously in dropout (100% duty cycle), and both channels draw a total quiescent cur- n PDAs/Palmtop PCs rent of only 40A. In shutdown, the device draws <1A. n Digital Cameras L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks n Cellular Phones of Linear Technology Corporation. All other trademarks are the property of their respective n owners. Protected by U.S. Patents, including 5481178, 6127815, 6304066, 6498466, 6580258 Portable Media Players 6611131.. n PC Cards n Wireless and DSL Modems TYPICAL APPLICATION Ef ciency and Power Loss vs Load Current V IN 2.8V TO 5.5V 100 1000 10F 100k RUN2 V RUN1 IN 95 MODE/SYNC POR RESET EFFICIENCY 90 100 LTC3548-2 85 V 4.7H 2.2H V OUT2 OUT1 POWER LOSS 2.5V SW2 SW1 1.8V 80 10 68pF 400mA 800mA 75 V = 3.6V IN V V OUT1 FB2 70 1 V = 1.8V OUT 887k Burst Mode OPERATION GND 280k 10F 4.7F 65 CHANNEL 1 NO LOAD ON CHANNEL 2 35482 F01 60 0.1 1 10 100 1000 Figure 1. 2.5V/1.8V at 400mA/800mA Step-Down Regulators LOAD CURRENT (mA) 35482 F01b 35482fb 1 EFFICIENCY (%)LTC3548-2 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) TOP VIEW V Voltages .................................................0.3V to 6V IN V 10 V 1 V , V Voltages ........................ 0.3V to V + 0.3V OUT1 FB2 OUT1 FB2 IN RUN1 2 9 RUN2 RUN1, RUN2 Voltages .................................0.3V to V IN 11 V 3 8 POR IN MODE/SYNC Voltage ........................ 0.3V to V + 0.3V IN SW1 4 7 SW2 SW1, SW2 Voltages ......................... 0.3V to V + 0.3V GND 5 6 MODE/ IN SYNC POR Voltage ................................................. 0.3V to 6V DD PACKAGE Ambient Operating Temperature Range 10-LEAD (3mm 3mm) PLASTIC DFN T = 125C, = 40C/W, = 3C/W (4-LAYER BOARD) JMAX JA JC (Note 2) ....................................................40C to 85C EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB GND Junction Temperature (Note 5) ............................. 125C Storage Temperature Range ................... 65C to 125C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3548EDD-2 PBF LTC3548EDD-2 TRPBF LCDK 40C to 85C 10-Lead (3mm 3mm) Plastic DFN Consult LTC Marketing for parts speci ed with wider operating temperature ranges. Consult LTC Marketing for information on non-standard lead based nish parts. For more information on lead free part marking, go to: