LTC3407-4 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}
LTC3407-4
Dual Synchronous, 800mA,
2.25MHz Step-Down
DC/DC Regulator
DESCRIPTIO
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 inductors
with a profile ≤1mm. 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.
The LTC3407-4 is identical to the LTC3407-2 except for
the reduced power-on reset delay time.
, 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
TYPICAL APPLICATIO
V_IN*
2.5V TO 5.5V
C1
10µF
V_OUT2
2.5V
800mA
L2
2.2µH
C5, 22pF
RUN2 V_IN RUN1
MODE/SYNC
POR
LTC3407-4
SW2
SW1
R5
100k
RESET
L1
2.2µH
C4, 22pF
V_OUT1
1.8V
800mA
C3
10µF
R4
887k R3
280k
V_FB2
GND
V_FB1
R2
R1 604k
301k
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
LTC3407-4 Efficiency/Power Loss Curve
100
90
80
70
60
50
40
30
20
10
0
0.1
1
0.1
0.01
0.001
1
10
100
LOAD CURRENT (mA)
0.0001
1000
34074 TA02
34074f
1