LTC3407A-2
Dual Synchronous 800mA,
2.25MHz Step-Down
DC/DC Regulator
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DESCRIPTIO
FEATURES
The LTC®3407A-2 is a dual, constant frequency, synchro-
nousstep-downDC/DCconverter. Intendedforlowpower
applications, it operates from a 2.5V to 5.5V input voltage
range and has a constant 2.25MHz switching frequency,
enabling the use of tiny, low cost capacitors and inductors
1mm or less in height. Each output voltage is adjustable
from 0.6V to 5V. Internal synchronous 0.35Ω, 1A power
switches provide high efficiency without the need for
external Schottky diodes.
■
High Efficiency: Up to 95%
■
Low Ripple (<35mVPK-PK) Burst Mode Operation;
IQ = 40μA
■
2.25MHz Constant Frequency Operation
■
No Schottky Diodes Required
■
Low RDS(ON) Internal Switches: 0.35Ω
■
Current Mode Operation for Excellent Line
and Load Transient Response
Short-Circuit Protected
■
■
Low Dropout Operation: 100% Duty Cycle
A user selectable mode input is provided to allow the user
to trade-off ripple noise for low power efficiency. Burst
Mode® operation provides the highest efficiency at light
loads, while Pulse Skip Mode provides the lowest ripple
noise at light loads.
■
Ultralow Shutdown Current: IQ <1μA
■
Output Voltages from 5V down to 0.6V
■
Power-On Reset Output
■
Externally Synchronizable Oscillator
■
Optional External Soft-Start
■
To further maximize battery life, the P-channel MOSFETs
are turned on continuously in dropout (100% duty cycle),
and both channels draw a total quiescent current of only
40μA. 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, 6304066, 6127815, 6498466, 6611131.
Small Thermally Enhanced MSOP and 3mm × 3mm
DFN Packages
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APPLICATIO S
■
PDAs/Palmtop PCs
■
Digital Cameras
■
Cellular Phones
Wireless and DSL Modems
■
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TYPICAL APPLICATIO
1mm High 2.5V/1.8V at 800mA Step-Down Regulators
Efficiency/Power Loss Curve
100
90
1
2.5V
V = 2.5V
IN
TO 5.5V
1.8V
80
100k
10μF
0.1
RUN/SS2
V
RUN/SS1
POR
IN
70
MODE/SYNC
RESET
60
LTC3407A-2
50
40
0.01
0.001
0.0001
2.2μH
2.2μH
V
OUT2
= 2.5V
V
= 1.8V
OUT1
SW2
SW1
AT 800mA
AT 800mA
22pF
887k
22pF
887k
30
20
V
= 3.3V
IN
Burst Mode OPERATION
V
FB1
V
FB2
10
0
NO LOAD ON OTHER CHANNEL
GND
280k
442k
10μF
10μF
1
10
100
1000
LOAD CURRENT (mA)
3407A2 TA02
3407A2 TA01
3407a2f
1