Datasheet LTC3620 (Analog Devices)

LTC3620 Ultralow Power 15mA Synchronous Step-Down Switching Regulator
FEATURES DESCRIPTION
n
High Effi ciency: Up to 95%
The LTC®3620 is a high effi 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 effi ciency n
18μA IQ Current
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 <1μA Supply Current n 2.8V Undervoltage Lockout The LTC3620 uses a unique variable frequency architecture n Unique Low Noise Control Architecture to minimize power loss and achieve high effi ciency. The n Internal Power MOSFETs switching frequency is proportional to the load current, and n No Schottky Diodes Required an internal frequency clamp forces a minimum switching n Internal Soft-Start frequency at light loads to minimize noise in the audio n Tiny 2mm range. The user can program the frequency of this clamp × 2mm 8-Lead DFN Package by applying an external clock to the FMIN/MODE pin.
APPLICATIONS
The battery status output, LOBATB, indicates when the 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 profi 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 Effi ciency Low Power Output Voltage Ripple Step-Down Converter vs Load Current Effi ciency vs Load Current
100 3.0 25 V V IN OUT = 1.1V 2.9V TO 5.5V FMIN/MODE = 0V 90 EFFICIENCY L = 22μH 2.5 20 80 VIN POWER LOSS (mW) 70 V RUN LOBATB 22μH ) IN = 5.5V 2.0 VOUT P-P 15 60 SW 1.1V 22pF 50 (mV 1.5 1μF LTC3620 VIN = 3.6V CER OUT 10 40 VIN = 3V V $ EFFICIENCY (%) FMIN/MODE = 0V FMIN/MODE V 1.0 FB 30 V 432k OUT = 1.1V GND 1μF V 523k 5 20 OUT = 1.8V CER V 0.5 OUT = 2.5V LOSS 10 3620 TA01a 0 0 0 0 5 10 15 0.1 1 10 OUTPUT CURRENT (mA) 3620 TA01b LOAD CURRENT (mA) 3620 TA01c 3620fa 1 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL CHARACTERISTICS TYPICAL PERFORMANCE CHARACTERISTICS PIN FUNCTIONS BLOCK DIAGRAM OPERATION APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION REVISION HISTORY TYPICAL APPLICATIONS RELATED PARTS