LTC3407-2 Datasheet, PDF (1/16 Pages) Linear Technology – Dual Synchronous, 800mA, 2.25MHz Step-Down DC/DC Regulator

FEATURES
■ _{High Efficiency: Up to 95%}
■ _{Very Low Quiescent Current: Only 40µA}
■ _{2.25MHz Constant Frequency Operation}
■ _{High Switch Current: 1.2A on Each Channel}
■ _{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}
■ _{Ultralow Shutdown Current: IQ < 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
U
APPLICATIO S
■ _{PDAs/Palmtop PCs}
■ _{Digital Cameras}
■ _{Cellular Phones}
■ _{Portable Media Players}
■ _{PC Cards}
■ _{Wireless and DSL Modems}
LTC3407-2
Dual Synchronous, 800mA,
2.25MHz Step-Down
DC/DC Regulator
DESCRIPTIO
The LTC^®3407-2 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 inductors
with a profile ≤1.2mm. Each output voltage is adjustable
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 Skip 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
V_IN = 2.5V*
TO 5.5V
C1
10µF
RUN2 V_IN RUN1
MODE/SYNC
POR
V_OUT2 = 2.5V
AT 800mA
L2
2.2µH
C5, 22pF
LTC3407-2
SW2
SW1
R5
100k
RESET
L1
2.2µH
C4, 22pF
C3
10µF
R4
887k R3
280k
V_FB2
GND
V_FB1
R2
R1 604k
301k
V_OUT1 = 1.8V
AT 800mA
C2
10µF
C1, C2, C3: TAIYO YUDEN JMK316BJ106ML
L1, L2: MURATA LQH32CN2R2M33
*V_OUT CONNECTED TO V_IN FOR V_IN ≤ 2.8V
Figure 1. 2.5V/1.8V at 800mA Step-Down Regulators
3407 TA01
LTC3407-2 Efficiency Curve
100
95
2.5V
90
1.8V
85
80
75
70
V_IN = 3.3V
65 _{Burst Mode OPERATION}
NO LOAD ON OTHER CHANNEL
60
1
10
100
LOAD CURRENT (mA)
1000
3407 TA02
sn34072 34072fs
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