POWER LOSS (mW) LTC3620 Ultralow Power 15mA Synchronous Step-Down Switching Regulator FEATURES DESCRIPTION n High Ef ciency: Up to 95% The LTC 3620 is a high ef ciency, synchronous buck n Maximum Current Output: 15mA regulator, suitable for very low power, very small footprint n Externally Programmable Frequency Clamp with applications powered by a single Li-Ion battery. Internal 50kHz Default Minimizes Audio Noise The internal synchronous switches increase ef ciency n 18A I Current Q and eliminate the need for external Schottky diodes. Low n 2.9V to 5.5V Input Voltage Range output voltages are easily supported by the 0.6V feedback n Low-Battery Detection reference voltage. The LTC3620-1 option is internally n 0.6V Reference Allows Low Output Voltages programmed to provide a 1.1V output. n Shutdown Mode Draws <1A Supply Current n The LTC3620 uses a unique variable frequency architecture 2.8V Undervoltage Lockout n to minimize power loss and achieve high ef ciency. The Unique Low Noise Control Architecture n switching frequency is proportional to the load current, and Internal Power MOSFETs n an internal frequency clamp forces a minimum switching No Schottky Diodes Required n frequency at light loads to minimize noise in the audio Internal Soft-Start n range. The user can program the frequency of this clamp Tiny 2mm 2mm 8-Lead DFN Package by applying an external clock to the FMIN/MODE pin. The battery status output, LOBATB, indicates when the APPLICATIONS input voltage drops below 3V. To help prevent damage to n Hearing Aids the battery, an undervoltage lockout (UVLO) circuit shuts n Wireless Headsets down the part if the input voltage falls below 2.8V. n Li-Ion Cell Applications The LTC3620 is available in a low pro le, 2mm 2mm n Button Cell Replacement 8-lead DFN package. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 7528587. TYPICAL APPLICATION High Ef ciency Low Power Output Voltage Ripple Step-Down Converter vs Load Current Ef ciency vs Load Current 100 3.0 25 V = 1.1V V OUT IN FMIN/MODE = 0V 90 EFFICIENCY 2.9V TO 5.5V L = 22H 2.5 80 20 V IN 70 V = 5.5V IN 2.0 RUN LOBATB 22H V 60 OUT 15 SW 1.1V 22pF 50 1.5 LTC3620 1F V = 3.6V IN V = 3V IN CER 40 10 FMIN/MODE = 0V 1.0 FMIN/MODE V FB 30 V = 1.1V OUT 432k GND 1F V = 1.8V OUT 523k 20 5 CER V = 2.5V 0.5 OUT LOSS 10 3620 TA01a 0 0 0 0.1 110 0 5 10 15 3620 TA01c OUTPUT CURRENT (mA) 3620 TA01b LOAD CURRENT (mA) 3620fa 1 V (mV ) OUT P-P EFFICIENCY (%)LTC3620 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) Input Supply Voltage .................................... 0.3V to 6V RUN Voltage ................................. 0.3V to (V + 0.3V) TOP VIEW IN V Voltage ................................... 0.3V to (V + 0.3V) FB IN SW 1 8 V IN LOBATB Voltage ........................................... 0.3V to 6V GND 2 7 RUN 9 FMIN/MODE Voltage ..................... 0.3V to (V + 0.3V) GND FMIN/MODE 3 6 V IN FB SW Voltage .................................. 0.3V to (V + 0.3V) LOBATB 4 5 NC IN P-channel Switch Source Current (DC) ..................50mA DC PACKAGE 8-LEAD (2mm 2mm) PLASTIC DFN N-channel Switch Sink Current (DC) ......................50mA T = 125C, = 88.5C/W JMAX JA Operating Junction Temperature Range EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB (Note 2) ..................................................40C to 125C Storage Temperature Range ...................65C to 150C ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC3620EDC PBF LTC3620EDC TRPBF LFJJ 40C to 85C 8-Lead (2mm 2mm) Plastic DFN LTC3620EDC-1 PBF LTC3620EDC-1 TRPBF LFJK 40C to 85C 8-Lead (2mm 2mm) 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: