LTC3407-2_15 Datasheet, PDF (1/16 Pages) Linear Technology – Dual Synchronous, 800mA, 2.25MHz Step-Down DC/DC Regulator

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}
LTC3407-2
Dual Synchronous, 800mA,
2.25MHz Step-Down
DC/DC Regulator
DESCRIPTION
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-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.
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.
TYPICAL APPLICATION
V_IN = 2.5V*
TO 5.5V
C1
10μF
V_OUT2 = 2.5V
AT 800mA
L2
2.2μH
C5, 22pF
RUN2 V_IN RUN1
MODE/SYNC
POR
LTC3407-2
SW2
SW1
R5
100k
RESET
L1
2.2μH
C4, 22pF
C3
10μF
R4
887k R3
V_FB2
GND
V_FB1
R2
R1 604k
280k
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 b 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
65
V_IN = 3.3V
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
60
1
10
100
LOAD CURRENT (mA)
1000
3407 TA02
34072fc
1