LTC3417 Datasheet, PDF (1/20 Pages) Linear Technology – Dual Synchronous 1.4A/800mA 4MHz Step-Down DC/DC Regulator

LTC3417
Dual Synchronous
1.4A/800mA 4MHz
Step-Down DC/DC Regulator
FEATURES
■ _{High Efficiency: Up to 95%}
■ _{1.4A/800mA Guaranteed Minimum Output Current}
■ _{No Schottky Diodes Required}
■ _{Programmable Frequency Operation: 1.5MHz or}
Adjustable From 0.6MHz to 4MHz
■ _{Low RDS(ON) Internal Switches}
■ _{Short-Circuit Protected}
■ _{VIN: 2.25V to 5.5V}
■ _{Current Mode Operation for Excellent Line and Load}
Transient Response
■ _{125µA Quiescent Current in Sleep Mode}
■ _{Ultralow Shutdown Current: IQ < 1µA}
■ _{Low Dropout Operation: 100% Duty Cycle}
■ _{Power Good Output}
■ _{Phase Pin Selects 2nd Channel Phase Relationship}
with Respect to 1st Channel
■ _{Internal Soft-Start with Individual Run Pin Control}
■ _{Available in Small Thermally Enhanced}
(5mm × 3mm) DFN and 20-Lead TSSOP Packages
U
APPLICATIO S
■ _{PDAs/Palmtop PCs}
■ _{Digital Cameras}
■ _{Cellular Phones}
■ _{PC Cards}
■ _{Wireless and DSL Modems}
DESCRIPTIO
The LTC^®3417 is a dual constant frequency, synchronous
step-down DC/DC converter. Intended for medium power
applications, it operates from a 2.25V to 5.5V input voltage
range and has a constant programmable switching fre-
quency, allowing the use of tiny, low cost capacitors and
inductors 2mm or less in height. Each output voltage is
adjustable from 0.8V to 5V. Internal synchronous low
R_DS(ON) power switches provide high efficiency without
the need for external Schottky diodes.
A user selectable mode input allows the user to trade off
ripple voltage for light load efficiency. Burst Mode^® opera-
tion provides high efficiency at light loads, while Pulse
Skip mode provides low ripple noise at light loads. A phase
mode pin allows the second channel to operate in-phase
or 180° out-of-phase with respect to channel 1. Out-of-
phase operation produces lower RMS current on V_IN and
thus lower RMS derating on the input capacitor.
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
125µA. In shutdown, the device draws <1µA.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark 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, 6144194
TYPICAL APPLICATIO
V_IN
2.5V TO 5.5V
V_OUT1
1.8V
1.4A
22µF
10µF
1.5µH
22pF
V_IN
511k
412k
5.9k
2200pF
V_IN
FREQ
SW1
SW2
RUN1
RUN2
LTC3417
V_FB1
V_FB2
I_TH1
I_TH2
GND
2.2µH
V_IN
22pF
866k
412k
2.87k
6800pF
3417 TA01
V_OUT2
2.5V
800mA
10µF
OUT2 Efficiency
(Burst Mode Operation)
100 _{REFER TO FIGURE 4}
10
95
1
EFFICIENCY
90
0.1
85
0.01
80
POWER LOSS
75
70
0.001
0.001
V_IN = 3.6V
V_OUT = 2.5V
FREQ = 1MHz _0.0001
0.01
0.1
1
LOAD CURRENT (A)
3417 TA01a
3417fb
1