LTC3729
550kHz, PolyPhase,
High Efficiency, Synchronous
Step-Down Switching Regulator
DESCRIPTION
FEATURES
The LTC®3729 is a multiple phase, synchronous
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Wide V Range: 4V to 36V Operation
IN
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Reduces Required Input Capacitance and Power
step‑down current mode switching regulator controller
that drives N‑channel external power MOSFET stages in a
phase‑lockablefixedfrequencyarchitecture.ThePolyPhase
controller drives its two output stages out of phase at
frequencies up to 550kHz to minimize the RMS ripple
currents in both input and output capacitors. The output
clock signal allows expansion for up to 12 evenly phased
controllers for systems requiring 15A to 200A of output
current.Themultiplephasetechniqueeffectivelymultiplies
the fundamental frequency by the number of channels
used, improving transient response while operating each
channel at an optimum frequency for efficiency. Thermal
design is also simplified.
Supply Induced Noise
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±1% Output Voltage Accuracy
Phase-Lockable Fixed Frequency: 250kHz to 550kHz
True Remote Sensing Differential Amplifier
PolyPhase® Extends from Two to Twelve Phases
Reduces the Size and Value of Inductors
Current Mode Control Ensures Current Sharing
1.1MHz Effective Switching Frequency (2‑Phase)
OPTI‑LOOP® Compensation Reduces C
OUT
Power Good Output Voltage Indicator
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Soft‑Start Current Ramping
Internal Current Foldback Plus Shutdown Timer
Overvoltage Soft‑Latch Eliminates Nuisance Trips
Available in 5mm × 5mm QFN
Aninternaldifferentialamplifierprovidestrueremotesens‑
ing of the regulated supply’s positive and negative output
terminals as required for high current applications.
and 28‑Lead SSOP Packages
A RUN/SS pin provides both soft‑start and optional timed,
short‑circuit shutdown. Current foldback limits MOSFET
dissipation during short‑circuit conditions when the
overcurrentlatchoffisdisabled.OPTI‑LOOPcompensation
allows the transient response to be optimized over a wide
range of output capacitance and ESR values. The LTC3729
includes a power good output pin that indicates when the
output is within ±7.5% of the designed set point.
APPLICATIONS
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Desktop Computers/Servers
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Large Memory Arrays
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DC Power Distribution Systems
L, LT, LTC, LTM, PolyPhase, OPTI‑LOOP, Linear Technology and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
TYPICAL APPLICATION
V
IN
5V TO 28V
0.1µF
10Ω
S
10µF
35V
CERAMIC
×4
M1
S
LTC3729
V
TG1
BOOST1
SW1
IN
0.002Ω
0.47µF
0.1µF
L1
0.8µH
S
M2
×2
D1
RUN/SS
PGOOD
BG1
PGND
+
SENSE1
SENSE1
I
TH
–
3.3k
16k
1000pF
16k
M3
TG2
BOOST2
SW2
S
S
S
0.002Ω
SGND
V
OUT
1.6V/40A
0.47µF
L2
0.8µH
S
S
S
M4
×2
V
BG2
DIFFOUT
D2
EAIN
–
INTV
CC
+
10µF
+
C
OUT
V
V
SENSE2
SENSE2
OS
OS
1000µF ×2
+
–
4V
C
: T510E108K004AS
L1, L2: CEPH149-IROMC
M1, M3: IRF7811W
M2, M4: IRF7822
OUT
3729 TA01
D1, D2: UP5840
Figure 1. High Current Dual Phase Step-Down Converter
3729fb
1