FEATURES
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LTC3732
3-Phase, 5-Bit VID,
600kHz, Synchronous Buck
Switching Regulator Controller
DESCRIPTIO
The LTC
®
3732 is a PolyPhase
®
synchronous step-down
switching regulator controller that drives all N-channel
external power MOSFET stages in a phase-lockable fixed
frequency architecture. The 3-phase controller drives its
output stages with 120° phase separation at frequencies
of up to 600kHz per phase to minimize the RMS current
losses in both the input and output filter capacitors. The 3-
phase technique effectively triples the fundamental fre-
quency, improving transient response while operating
each controller at an optimal frequency for high efficiency
and ease of thermal design. Light load efficiency is opti-
mized by using a choice of output Stage Shedding or Burst
Mode technology.
A differential amplifier provides true remote sensing of both
the high and low side of the output voltage at load points.
Soft-start and a defeatable, timed short-circuit shutdown
protect the MOSFETs and the load. A foldback current
circuit also provides protection for the external MOSFETs
under short-circuit or overload conditions.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode, OPTI-LOOP and PolyPhase are registered trademarks of Linear Technology
Corporation. Stage Shedding is a trademark of Linear Technology Corporation
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3-Phase Current Mode Controller with
Onboard MOSFET Drivers
±5%
Output Current Matching Optimizes Thermal
Performance and Size of Inductors and MOSFETs
4.5V
≤
V
CC
≤
7V; 4.5V
≤
V
IN
≤
32V
Differential Amplifier Accurately Senses V
OUT
Reduced Input and Output Capacitance
Reduced Power Supply Induced Noise
VID DAC Programmable from 1.1V to 1.85V
(VRM9.0/9.1)
±10%
Power Good Output Indicator
250kHz to 600kHz Per Phase, PLL, Fixed Frequency
PWM, Stage Shedding
TM
or Burst Mode
®
Operation
OPTI-LOOP
®
Compensation Minimizes C
OUT
Adjustable Soft-Start Current Ramping
Short-Circuit Shutdown Timer with Defeat Option
Overvoltage Soft Latch
Small 36-Lead Narrow (0.209") SSOP Package
QFN 5mm
×
7mm 38-Lead Package
Desktop Computers
High Performance Notebook Computers
High Output Current DC/DC Power Supplies
APPLICATIO S
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TYPICAL APPLICATIO
V
CC
4.5V TO 7V
V
CC
10µF
LTC3732
BOOST1
BOOST2
BOOST3
0.1µF
SW3 SW2 SW1
TG1
SW1
BG1
SENSE1
+
SENSE1
–
TG2
SW2
BG2
PGND
SENSE2
+
SENSE2
–
TG3
SW3
BG3
SENSE3
+
SENSE3
–
V
IN
V
IN
1µH
0.003Ω
POWER GOOD INDICATOR
OPTIONAL SYNC IN
PGOOD
PLLIN
PLLFLTR
1µH
0.003Ω
5 VID BITS
680pF
VID0-VID4
I
TH
5k
0.1µF
RUN/SS
SGND
EAIN
IN
–
IN
+
1µH
0.003Ω
100pF
Figure 1. High Current Triple Phase Step-Down Converter
3732f
U
U
U
+
V
IN
5V TO 28V
22µF
35V
V
OUT
1.1V TO 1.85V
55A
+
C
OUT
470µF
4V
3732 F01
1
LINER [ LINEAR TECHNOLOGY ]
