LTC3609
32V, 6A Monolithic
Synchronous Step-Down
DC/DC Converter
FEATURES
DESCRIPTION
TheLTC®3609isahighefficiency,monolithicsynchronous
step-downDC/DCconverterthatcandeliverupto6Aoutput
current from a 4V to 32V (36V maximum) input supply. It
uses a valley current control architecture to deliver very
low duty cycle operation at high frequency with excellent
transient response. The operating frequency is selected
by an external resistor and is compensated for variations
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6A Output Current
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Wide V Range = 4V to 32V (36V Maximum)
IN
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Internal N-Channel MOSFETs
True Current Mode Control
Optimized for High Step-Down Ratios
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t
≤ 100ns
ON(MIN)
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Extremely Fast Transient Response
Stable with Ceramic C
in V and V
.
OUT
IN
OUT
1ꢀ 0ꢁ6V Voltage Reference
Power Good Output Voltage Monitor
Adjustable On-Time/Switching Frequency
Adjustable Current Limit
Programmable Soft-Start
Output Overvoltage Protection
Optional Short-Circuit Shutdown Timer
The LTC3609 can be configured for discontinuous or
forced continuous operation at light load. Forced continu-
ous operation reduces noise and RF interference while
discontinuous mode provides high efficiency by reducing
switching losses at light loads.
Fault protection is provided by internal foldback current
limiting,anoutputovervoltagecomparatorandanoptional
short-circuit shutdown timer. Soft-start capability for sup-
ply sequencing is accomplished using an external timing
capacitor.Theregulatorcurrentlimitisuserprogrammable.
A power good output voltage monitor indicates when
the output is in regulation. The LTC3609 is available in a
compact 7mm × 8mm QFN package.
Low Shutdown I : 15μA
Available in a 7mm × 8mm 52-Pin QFN Package
Q
APPLICATIONS
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Point of Load Regulation
Distributed Power Systems
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L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents, including
5481178, 6100678, 6580258, 5847554, 6304066.
TYPICAL APPLICATION
Efficiency and Power Loss vs
Load Current
High Efficiency Step-Down Converter
187k
V
V
I
ON
100
90
80
70
60
50
40
30
20
10
0
10000
1000
100
10
0.1μF OUT
ON
V
EFFICIENCY
IN
4V TO 32V
RUN/SS
V
IN
10μF
x3
100pF
LTC3609
1.2μH
V
2.5V
6A
OUT
SW
1000pF
15.8k
0.22μF
100μF
x2
I
BOOST
POWER LOSS
TH
SGND INTV
CC
30.1k
9.53k
FCB
V
IN
IN
= 12V
= 25V
V
= 2.5V
CC
OUT
EXTV = 5V
4.7μF
V
RNG
V
PGND
1
PGOOD
0.01
0.1
1
10
EXTV
CC
V
FB
LOAD CURRENT (A)
3609 TA01b
3609 TA01a
3609f
1