LTC3729_15 Datasheet, PDF (1/30 Pages) Linear Technology – 550kHz, PolyPhase, High Efficiency, Synchronous Step-Down Switching Regulator

LTC3729
FEATURES
550kHz, PolyPhase,
High Efficiency, Synchronous
Step-Down Switching Regulator
DESCRIPTION
n _{Wide VIN Range: 4V to 36V Operation}
n _{Reduces Required Input Capacitance and Power}
Supply Induced Noise
n _{±1% Output Voltage Accuracy}
n _{Phase-Lockable Fixed Frequency: 250kHz to 550kHz}
n _{True Remote Sensing Differential Amplifier}
n _PolyPhase^® _{Extends from Two to Twelve Phases}
n _{Reduces the Size and Value of Inductors}
n _{Current Mode Control Ensures Current Sharing}
n _{1.1MHz Effective Switching Frequency (2-Phase)}
n _OPTI-LOOP^® _{Compensation Reduces COUT}
n _{Power Good Output Voltage Indicator}
n _{Very Low Dropout Operation: 99% Duty Cycle}
n _{Adjustable Soft-Start Current Ramping}
n _{Internal Current Foldback Plus Shutdown Timer}
n _{Overvoltage Soft-Latch Eliminates Nuisance Trips}
n _{Available in 5mm × 5mm QFN}
and 28-Lead SSOP Packages
APPLICATIONS
n _{Desktop Computers/Servers}
n _{Large Memory Arrays}
n _{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.
The LTC^®3729 is a multiple phase, synchronous
step‑down current mode switching regulator controller
that drives N‑channel external power MOSFET stages in a
phase‑lockable fixed frequency architecture. 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. The multiple phase 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.
An internal differential amplifier provides true remote sens‑
ing of the regulated supply’s positive and negative output
terminals as required for high current applications.
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 compensation
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.
TYPICAL APPLICATION
0.1µF
0.1µF
V_IN ^LTC3729 TG1
BOOST1
SW1
RUN/SS
BG1
PGOOD
I_TH
3.3k _1000pF
PGND
SENSE1⁺
SENSE1^–
TG2
SGND
BOOST2
16k
SW2
V_DIFFOUT
BG2
EAIN
INTV_CC
16k
V_OS–
SENSE2⁺
V_OS+
SENSE2^–
10Ω
0.47µF
0.47µF
10µF
M1
0.002Ω
M2
×2
D1
L1
0.8µH
M3
0.002Ω
L2
M4
0.8µH
×2
D2
C_OUT: T510E108K004AS
D1, D2: UP5840
L1, L2: CEPH149-IROMC
M1, M3: IRF7811W
M2, M4: IRF7822
Figure 1. High Current Dual Phase Step-Down Converter
10µF
35V
CERAMIC
×4
V_IN
5V TO 28V
V_OUT
1.6V/40A
+ C_OUT
1000µF ×2
4V
3729 TA01
3729fb
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