LTC3565
1.25A, 4MHz, Synchronous
Step-Down DC/DC Converter
FEATURES
DESCRIPTION
The LTC®3565 is a constant frequency, synchronous
step-down DC/DC converter. Intended for medium power
applications, it operates from a 2.5V to 5.5V input voltage
range and has a user configurable operating frequency
up to 4MHz, allowing the use of tiny, low cost capacitors
and inductors 1mm or less in height. The output voltage is
adjustablefrom0.6Vto5.5V. Internalsynchronouspower
switches provide high efficiency. The LTC3565’s current
mode architecture and external compensation allow the
transient response to be optimized over a wide range of
loads and output capacitors.
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High Efficiency: Up to 95%
IN
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V Range: 2.5V to 5.5V
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High Frequency Operation: Up to 4MHz
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Selectable Low Ripple (Typical 25mV
)
p-p
Burst Mode® Operation: I = 40μA
Q
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Stable with Ceramic Capacitors
Uses Tiny Capacitors and Inductor
Low R
Internal Switches: 0.15Ω
DS(ON)
Current Mode Operation for Excellent Line
and Load Transient Response
Short-Circuit Protected
Low Dropout Operation: 100% Duty Cycle
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The LTC3565 can be configured for automatic power
saving Burst Mode operation (I = 40μA) to reduce gate
charge losses when the load current drops below the level
required for continuous operation. For reduced noise and
RF interference, the SYNC/MODE pin can be configured to
skip pulses or provide forced continuous operation.
Low Shutdown Current: I ≤ 1μA
Q
Q
Output Voltages from 0.6V to 5V
Synchronizable to External Clock
Supports Pre-Biased Outputs
Small 10-Lead (3mm × 3mm) DFN or MSOP Package
To further maximize battery life, the P-channel MOSFET
is turned on continuously in dropout (100% duty cycle).
In shutdown, the device draws <1μA.
, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology
Corporation. All other trademarks are the property of their respective owners. Protected by
U.S. Patents, including 5481178, 6580258, 6498466, 6611131.
APPLICATIONS
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Notebook Computers
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Digital Cameras
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Cellular Phones
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Handheld Instruments
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Board Mounted Power Supplies
TYPICAL APPLICATION
Efficiency and Power Loss vs Output Current
Step-Down 2.5V/1.25A Regulator
100
90
80
70
60
50
40
30
20
10
0
1
V
IN
2.5V TO 5.5V
22μF
0.1
SV PV
IN
IN
SYNC/MODE
RUN
2.2μH
V
OUT
0.01
0.001
SW
PGOOD
2.5V
LTC3565
1.25A
ITH
RT
22μF
22pF
12.1k
V
V
V
= 2.7V
= 3.6V
= 4.2V
IN
IN
IN
V
FB
931k
294k
GND
680pF
0.0001
10000
191k
0.1
1
10
100
1000
OUTPUT CURRENT (mA)
3565 TA01a
3565 TA01b
3565f
1