LTC3620
Ultralow Power 15mA
Synchronous Step-Down
Switching Regulator
DESCRIPTION
FEATURES
The LTC®3620 is a high efficiency, synchronous buck
regulator, suitable for very low power, very small footprint
applications powered by a single Li-Ion battery.
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High Efficiency: Up to 95%
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Maximum Current Output: 15mA
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Externally Programmable Frequency Clamp with
Internal 50kHz Default Minimizes Audio Noise
The internal synchronous switches increase efficiency
and eliminate the need for external Schottky diodes. Low
output voltages are easily supported by the 0.6V feedback
reference voltage. The LTC3620-1 option is internally
programmed to provide a 1.1V output.
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18μA I Current
Q
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2.9V to 5.5V Input Voltage Range
Low-Battery Detection
0.6V Reference Allows Low Output Voltages
Shutdown Mode Draws <1μA Supply Current
2.8V Undervoltage Lockout
TheLTC3620usesauniquevariablefrequencyarchitecture
to minimize power loss and achieve high efficiency. The
switchingfrequencyisproportionaltotheloadcurrent,and
an internal frequency clamp forces a minimum switching
frequency at light loads to minimize noise in the audio
range. The user can program the frequency of this clamp
by applying an external clock to the FMIN/MODE pin.
Unique Low Noise Control Architecture
Internal Power MOSFETs
No Schottky Diodes Required
Internal Soft-Start
Tiny 2mm × 2mm 8-Lead DFN Package
The battery status output, LOBATB, indicates when the
input voltage drops below 3V. To help prevent damage to
the battery, an undervoltage lockout (UVLO) circuit shuts
down the part if the input voltage falls below 2.8V.
APPLICATIONS
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Hearing Aids
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Wireless Headsets
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Li-Ion Cell Applications
The LTC3620 is available in a low profile, 2mm × 2mm
8-lead DFN package.
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Button Cell Replacement
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
Output Voltage Ripple
vs Load Current
High Efficiency Low Power
Step-Down Converter
25
Efficiency vs Load Current
100
90
3.0
2.5
2.0
1.5
1.0
0.5
0
V
= 1.1V
OUT
V
IN
2.9V TO 5.5V
FMIN/MODE = 0V
L = 22μH
EFFICIENCY
80
20
15
10
5
V
IN
70
V
= 5.5V
IN
22μH
22pF
RUN
LOBATB
SW
V
60
50
OUT
1.1V
LTC3620
1μF
CER
V
= 3.6V
IN
V
= 3V
IN
FMIN/MODE = 0V
40
30
20
10
0
FMIN/MODE V
GND
FB
V
V
V
= 1.1V
= 1.8V
= 2.5V
OUT
OUT
OUT
432k
523k
1μF
CER
LOSS
3620 TA01a
0
0.1
1
10
0
5
10
15
3620 TA01c
LOAD CURRENT (mA)
OUTPUT CURRENT (mA)
3620 TA01b
3620f
1