Linear LTC3417A-1 Manual

FEATURES
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High Effi ciency: Up to 95%
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1.5A/1A Guaranteed Minimum Output Current
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Synchronizable to External Clock
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Power-On-Reset Output
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No Schottky Diodes Required
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Programmable Frequency Operation: 1.5MHz or
Adjustable From 0.6MHz to 4MHz
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Low Ripple (< 35mV
P-P
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Low R Internal Switches
DS(ON)
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Short-Circuit Protected
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V : 2.25V to 5.5V
IN
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Current Mode Operation for Excellent Line and Load
Transient Response
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125μA Quiescent Current in Sleep Mode
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Ultralow Shutdown Current: I
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Low Dropout Operation: 100% Duty Cycle
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Phase Pin Selects 2nd Channel Phase Relationship
with Respect to 1st Channel
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Internal Soft-Start with Individual Run Pin Control
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Available in Small Thermally Enhanced
(3mm × 5mm) DFN and 20-Lead TSSOP Packages
APPLICATIONS
GPS/Navigation Systems
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Automotive Instrumentation
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PC Cards
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Industrial Power Supplies
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General Purpose Point of Load DC/DC
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TYPICAL APPLICATION

V
IN
2.5V TO 5.5V
10μF
FREQ
1.5μH
V
OUT1
1.8V SW1
22pF
1.5A
V RUN1
IN
511k
V
FB1
47μF 412k
I
TH1
5.9k
2200pF
) BurstMode ® Operation
< 1μA
Q
100k
V
IN
POR RESET
2.2μH
SW2
22pF
RUN2
V
IN
LTC3417A-1
866k
V
FB2
412k
I
TH2
2.87k
GND
6800pF
3417A-1 TA01
1.5A/1A 4MHz Step-Down
DC/DC Regulator with POR
DESCRIPTION
The LTC ® 3417A-1 is a dual constant frequency, synchro-
nous 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
frequency, 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 power switches provide high effi ciency without
DS(ON)
the need for external Schottky diodes.
The open drain POR pin goes low when either output
voltage falls 6% below regulation. The output will remain
low 150ms longer than the duration of the out of regula-
tion condition.
A user selectable mode input allows the user to trade
off ripple voltage for light load effi ciency. Burst Mode
operation provides high effi ciency 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 and thus lower stress on the input capacitor.
IN
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
100μA. In shutdown, the device draws <1μA.
L, LT, LTC and 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, 6144194.
100
95
V
OUT2
90
2.5V
1A
85
80
22μF
75
70
0.001
LTC3417A-1
Dual Synchronous
OUT2 Effi ciency
(Burst Mode Operation)
10
REFER TO FIGURE 4
1
EFFICIENCY
0.1
0.01
POWER LOSS
0.001
V = 3.6V
IN
V = 2.5V
OUT
FREQ = 1MHz
0.0001
0.01 0.1 1
LOAD CURRENT (A)
3417A-1 TA01a 3417a1fa
1