LTC3407A-2 Datasheet, PDF (1/16 Pages) Linear Technology – Dual Synchronous 800mA,2.25MHz Step-Down DC/DC Regulator

FEATURES
■ _{High Efficiency: Up to 95%}
■ _{Low Ripple (<35mVPK-PK) Burst Mode Operation;}
I_Q = 40μA
■ _{2.25MHz Constant Frequency Operation}
■ _{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}
■ _{Optional External Soft-Start}
■ _{Small Thermally Enhanced MSOP and 3mm × 3mm}
DFN Packages
U
APPLICATIO S
■ _{PDAs/Palmtop PCs}
■ _{Digital Cameras}
■ _{Cellular Phones}
■ _{Wireless and DSL Modems}
LTC3407A-2
Dual Synchronous 800mA,
2.25MHz Step-Down
DC/DC Regulator
DESCRIPTIO
The LTC^®3407A-2 is a dual, constant frequency, synchro-
nous step-down DC/DC converter. Intended for low power
applications, it operates from a 2.5V to 5.5V input voltage
range and has a constant 2.25MHz switching frequency,
enabling the use of tiny, low cost capacitors and inductors
1mm 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 the highest efficiency at light
loads, while Pulse Skip Mode provides the lowest 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.
, 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
1mm High 2.5V/1.8V at 800mA Step-Down Regulators
V_IN = 2.5V
TO 5.5V
10μF
V_OUT2 = 2.5V
AT 800mA
2.2μH
22pF
RUN/SS2 V_IN
MODE/SYNC
RUN/SS1
POR
LTC3407A-2
SW2
SW1
100k
RESET
2.2μH
22pF
V_OUT1 = 1.8V
AT 800mA
10μF
887k
280k
V_FB2
GND
V_FB1
887k
442k
10μF
3407A2 TA01
Efficiency/Power Loss Curve
100
90
80
70
60
50
40
30
20
10
0
1
1
2.5V
1.8V
0.1
0.01
0.001
V_IN = 3.3V
Burst Mode OPERATION
NO LOAD ON OTHER CHANNEL
0.0001
10
100
1000
LOAD CURRENT (mA)
3407A2 TA02
3407a2f
1