LTC3407
Dual Synchronous, 600mA,
1.5MHz Step-Down
DC/DC Regulator
FEATURES
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DESCRIPTIO
High Efficiency: Up to 96%
Very Low Quiescent Current: Only 40µA
1.5MHz Constant Frequency Operation
High Switch Current: 1A on Each Channel
No Schottky Diodes Required
Low R
DS(ON)
Internal Switches: 0.35Ω
Current Mode Operation for Excellent Line
and Load Transient Response
Short-Circuit Protected
Low Dropout Operation: 100% Duty Cycle
Ultralow Shutdown Current: I
Q
< 1µA
Output Voltages from 5V down to 0.6V
Power-On Reset Output
Externally Synchronizable Oscillator
Small Thermally Enhanced MSOP and 3mm
×
3mm
DFN Packages
The LTC
®
3407 is a dual, constant frequency, synchronous
step down DC/DC converter. Intended for low power
applications, it operates from 2.5V to 5.5V input voltage
range and has a constant 1.5MHz switching frequency,
allowing the use of tiny, low cost capacitors and inductors
2mm 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.
A user selectable mode input is provided to allow the user
to trade-off ripple noise for low power efficiency. Burst
Mode
®
operation provides high efficiency at light loads,
while Pulse Skip Mode provides low ripple noise at light
loads.
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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
APPLICATIO S
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PDAs/Palmtop PCs
Digital Cameras
Cellular Phones
Portable Media Players
PC Cards
Wireless and DSL Modems
TYPICAL APPLICATIO
V
IN
= 2.5V
TO 5.5V
C1
10µF
RUN2
V
IN
RUN1
POR
R5
100k
RESET
MODE/SYNC
L2
2.2µH
SW2
C5, 22pF
LTC3407
EFFICIENCY (%)
V
OUT2
= 2.5V
AT 600mA
L1
2.2µH
SW1
C4, 22pF
V
OUT1
= 1.8V
AT 600mA
C3
10µF
R4
887k
V
FB2
R3
280k
GND
V
FB1
R1
442k
R2
887k
C2
10µF
C1, C2, C3: TAIYO YUDEN JMK316BJ106ML
L1, L2: MURATA LQH32CN2R2M33
3407 TA01
Figure 1. 2.5V/1.8V at 600mA Step-Down Regulators
sn3407 3407fs
U
LTC3407 Efficiency Curve
100
95
90
85
80
75
70
65
60
1
V
IN
= 3.3V
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
10
100
LOAD CURRENT (mA)
1000
3407 TA02
U
U
2.5V
1.8V
1
LINER [ LINEAR TECHNOLOGY ]
