FEATURES
n High Efficiency: Up to 95%
n Very Low Quiescent Current: Only 40μA
n 2.25MHz Constant Frequency Operation
n High Switch Current: 1.2A on Each Channel
n No Schottky Diodes Required
n Low RDS(ON) Internal Switches: 0.35Ω
n Current Mode Operation for Excellent Line
and Load Transient Response
n Short-Circuit Protected
n Low Dropout Operation: 100% Duty Cycle
n Ultralow Shutdown Current: IQ < 1μA
n Output Voltages from 5V down to 0.6V
n Power-On Reset Output
n Externally Synchronizable Oscillator
n Small Thermally Enhanced MSOP and 3mm × 3mm
DFN Packages
APPLICATIONS
n PDAs/Palmtop PCs
n Digital Cameras
n Cellular Phones
n Portable Media Players
n PC Cards
n Wireless and DSL Modems
LTC3407-4
Dual Synchronous, 800mA,
2.25MHz Step-Down
DC/DC Regulator
DESCRIPTION
The LTC®3407-4 is a dual, constant frequency, synchro-
nous 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 2.25MHz switching frequency,
allowing the use of tiny, low cost capacitors and induc-
tors with a profile ≤1mm. Each output voltage is adjust-
able from 0.6V to 5V. Internal synchronous 0.35Ω, 1.2A
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 noise ripple for low power efficiency. Burst
Mode® operation provides high efficiency at light loads,
while pulse-skipping mode provides low noise ripple 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.
The LTC3407-4 is identical to the LTC3407-2 except for
the reduced power-on reset delay time.
L, LT, LTC, LTM, Burst Mode, 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 5481178, 6580258, 6304066, 6127815, 6498466,
6611131.
TYPICAL APPLICATION
VIN*
2.5V TO 5.5V
C1
10μF
VOUT2
2.5V
800mA
L2
2.2μH
C5, 22pF
RUN2 VIN RUN1
MODE/SYNC
POR
LTC3407-4
SW2
SW1
R5
100k
RESET
L1
2.2μH
C4, 22pF
VOUT1
1.8V
800mA
C3
10μF
R4
887k R3
280k
VFB2
GND
VFB1
R2
R1 604k
301k
C2
10μF
C1, C2, C3: TAIYO YUDEN JMK316BJ106ML
L1, L2: MURATA LQH32CN2R2M33
*VOUT CONNECTED TO VIN FOR VIN ≤ 2.8V
Figure 1. 2.5V/1.8V at 800mA Step-Down Regulators
3407 TA01
LTC3407-4 Efficiency/Power Loss Curve
100
1
90
80
0.1
70
60
50
0.01
40
30
0.001
20
10
0
0.1
1
0.0001
10
100
1000
LOAD CURRENT (mA)
34074 TA02
34074fa
1
