LTC3565
1.25A, 4MHz, Synchronous
Step-Down DC/DC Converter
FEATURES
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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
adjustable from 0.6V to 5.5V. Internal synchronous power
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.
The LTC3565 can be configured for automatic power
saving Burst Mode operation (I
Q
= 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.
To further maximize battery life, the P-channel MOSFET
is turned on continuously in dropout (100% duty cycle).
In shutdown, the device draws <1μA.
L,
LT, LTC, LTM, Linear Technology the Linear logo, Burst Mode and OPTI-LOOP are registered
trademarks of Linear Technology Corporation. Hot Swap and ThinSOT are 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.
High Efficiency: Up to 95%
V
IN
Range: 2.5V to 5.5V
High Frequency Operation: Up to 4MHz
Selectable Low Ripple (Typical 25mV
p-p
)
Burst Mode
®
Operation: I
Q
= 40μA
Stable with Ceramic Capacitors
Uses Tiny Capacitors and Inductor
Low R
DS(ON)
Internal Switches: 0.15Ω
Current Mode Operation for Excellent Line
and Load Transient Response
Short-Circuit Protected
Low Dropout Operation: 100% Duty Cycle
Low Shutdown Current: I
Q
≤ 1μA
Output Voltages from 0.6V to 5V
Synchronizable to External Clock
Supports Pre-Biased Outputs
Small 10-Lead (3mm
×
3mm) DFN or MSOP Package
APPLICATIONS
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Notebook Computers
Digital Cameras
Cellular Phones
Handheld Instruments
Board Mounted Power Supplies
TYPICAL APPLICATION
Step-Down 2.5V/1.25A Regulator
V
IN
2.5V TO 5.5V
22μF
EFFICIENCY (%)
SYNC/MODE SV
IN
PV
IN
RUN
PGOOD
ITH
RT
12.1k
V
FB
GND
680pF
191k
22pF
LTC3565
SW
2.2μH
V
OUT
2.5V
1.25A
22μF
Efficiency and Power Loss vs Output Current
100
90
80
70
60
50
40
30
20
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
1
100
1000
10
OUTPUT CURRENT (mA)
0.01
0.1
POWER LOSS (W)
1
0.001
931k
294k
10
0
0.1
0.0001
10000
3565 TA01b
3565 TA01a
3565fb
1
LINEAR [ LINEAR INTEGRATED SYSTEMS ]
