LTC3729L-6
PolyPhase, Synchronous
Step-Down Switching Regulator
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DESCRIPTIO
FEATURES
The LTC®3729L-6 is a PolyPhaseTM synchronous step-
down current mode switching regulator controller with a
0.6V reference that drives N-channel external power
MOSFET stages in a phase-lockable fixed frequency archi-
tecture. The PolyPhase 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. This PolyPhase technique
effectively multiplies 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.
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Reduces Required Input Capacitance and Power
Supply Induced Noise
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True Remote Sensing Differential Amplifier
0.6V, ±1% Voltage Reference Accuracy
PolyPhase Controller Operates from Two to Twelve
Phases
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Current Mode Control Ensures Current Sharing
Phase-Lockable Fixed Frequency: 250kHz to 550kHz
OPTI-LOOP® Compensation Reduces COUT
Power Good Output Voltage Monitor
Wide VIN Range: 4V to 30V Operation
Very Low Dropout Operation: 99% Duty Cycle
Adjustable Soft-Start Current Ramping
Internal Current Foldback Plus Shutdown Timer
Overvoltage Soft-Latch Eliminates Nuisance Trips
Micropower Shutdown
An internal differential amplifier provides true remote
sensing of the regulated supply’s positive and negative
output terminals as required for high current applications.
32-Lead 5mm ×U5mm Plastic QFN Package
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
overcurrent latchoff is disabled. OPTI-LOOP compensa-
tion allows the transient response to be optimized over a
wide range of output capacitance and ESR values. The
LTC3729L-6 includes a power good output pin that
indicates when the output voltage is inside the ±10%
tolerance window.
APPLICATIO S
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Desktop Computers
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Internet Servers
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Large Memory Arrays
DC Power Distribution Systems
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, LTC and LT are registered trademarks of Linear Technology Corporation.
OPTI-LOOP is a registered trademark of Linear Technology Corporation.
PolyPhase is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATIO
10Ω
V
IN
5V TO 15V
10µF ×6
35V
CERAMIC
0.1µF
M1
S
LTC3729L-6
TG1
V
IN
S
0.002Ω
BOOST1
SW1
0.47µF
0.1µF
L1
1µH
S
M2
RUN/SS
PGOOD
BG1
×2
D1
PGND
3300pF
+
SENSE1
I
TH
–
SENSE1
1.5k
CLKOUT
SGND
M3
TG2
BOOST2
SW2
S
0.002Ω
S
V
OUT
0.47µF
0.7V/40A
L2
S
S
10k
S
M4
×2
1µH
V
BG2
DIFFOUT
D2
S
EAIN
–
INTV
CC
+
10µF CER
X5R
+
C
OUT
V
OS
V
OS
SENSE2
SENSE2
60.4k
270µF ×4
+
–
2V
C
: T510E108K004AS
L1, L2: CEPH149-IROMC-H
M1, M3: Si7840DP
M2, M4: Si7440DP
OUT
3729L-6 TA01
D1, D2: SBM540
Figure 1. High Current Dual Phase Step-Down Converter
sn3729l6 3729l6fs
1