LTC3731_15 Datasheet, PDF (1/34 Pages) Linear Technology – 3-Phase, 600kHz, Synchronous Buck Switching Regulator Controller

LTC3731
3-Phase, 600kHz,
Synchronous Buck Switching
Regulator Controller
FEATURES
DESCRIPTION
n _{3-Phase Current Mode Controller with Onboard}
MOSFET Drivers
n _{±5% Output Current Matching Optimizes Thermal}
Performance and Size of Inductors and MOSFETs
n _{Differential Amplifier Accurately Senses VOUT}
n _{±1% VREF Accuracy Over Temperature}
n _{VOUT Range: 0.6V to 5.5V without Diffamp}
n _{VOUT Range: 0.6V to (VCC – 1.2V) with Diffamp}
n _{250kHz to 600kHz Per Phase, PLL, Fixed Frequency}
n _{PWM, Stage Shedding™ or Burst Mode}^® _Operation
n _OPTI-LOOP^® _{Compensation Minimizes COUT}
n _{Adjustable Soft-Start Current Ramping}
n _{Short-Circuit Shutdown Timer with Defeat Option}
n _{Overvoltage Soft Latch}
n _{Adjustable Undervoltage Lockout Threshold}
n _{Selectable Phase Output for Up to 12-Phase Operation}
n _{Available in 5mm × 5mm QFN and 36-Pin Narrow}
(0.209") SSOP Packages
APPLICATIONS
n _{Desktop Computers and Servers}
n _{High Performance Notebook Computers}
n _{High Output Current DC/DC Power Supplies}
The LTC^®3731 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 efficiency and ease of
thermal design. Light load efficiency is optimized by using a
choice of output Stage Shedding or Burst Mode operation.
A differential amplifier provides true remote sensing of
both the high and low side of the output voltage at the
point of load.
Soft-start and a defeatable, timed short-circuit shutdown
protect the MOSFETs and the load. Current foldback
provides protection for the external MOSFETs under
short-circuit or overload conditions.
L, LT, LTC, LTM, Bust Mode, OPTI-LOOP, PolyPhase, Linear Technology and the Linear logo
are registered and Stage Shedding is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents, including
5481178, 5929620, 6177787, 6144194, 6100678, 5408150, 6580258, 6462525, 630466,
5705919.
TYPICAL APPLICATION
V_CC
4.5V TO 7V
10µF
0.1µF
SW3 SW2 SW1
POWER GOOD INDICATOR
OPTIONAL SYNC IN
V_CC
TG1
LTC3731 _SW1
BOOST1
BOOST2
BG1
BOOST3
SENSE1⁺
SENSE1^–
PGOOD
TG2
PLLIN
SW2
PLLFLTR
BG2
36k
V_IN
12k
680pF
UVADJ
PGND
SENSE2⁺
SENSE2^–
5k
7.5k
6.04k
I_TH
0.01µF
100pF
RUN/SS
SGND
EAIN
DIFFOUT
IN^–
IN⁺
TG3
SW3
BG3
SENSE3⁺
SENSE3^–
0.8µH
0.003Ω
V_IN
+
5V TO 28V
22µF
35V
V_IN
0.8µH
0.003Ω
V_OUT
1.35V
55A
V_IN
0.8µH
0.003Ω
+ C_OUT
470µF
4V
3731 F01
Figure 1. High Current Triple Phase Step-Down Converter
3731fc
1