LTC3731 Datasheet, PDF (1/32 Pages) Linear Technology – 3-Phase, 600kHz, Synchronous Buck Switching Regulator Controller

LTC3731
3-Phase, 600kHz,
Synchronous Buck Switching
Regulator Controller
FEATURES
DESCRIPTIO
■ _{3-Phase Current Mode Controller with Onboard}
MOSFET Drivers
■ _{±5% Output Current Matching Optimizes Thermal}
Performance and Size of Inductors and MOSFETs
■ _{Differential Amplifier Accurately Senses VOUT}
■ _{±1% VREF Accuracy Over Temperature}
■ _{Reduced Power Supply Induced Noise}
■ _{±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 COUT}
■ _{Adjustable Soft-Start Current Ramping}
■ _{Short-Circuit Shutdown Timer with Defeat Option}
■ _{Overvoltage Soft Latch}
■ _{Adjustable Undervoltage Lockout Threshold}
■ _{Selectable Phase Output for Up to 12-Phase Operation}
■ _{Available in 5mm × 5mm QFN and 36-Pin Narrow}
(0.209") SSOP P_Uackages
APPLICATIO S
■ _{Desktop Computers and Servers}
■ _{High Performance Notebook Computers}
■ _{High Output Current DC/DC Power Supplies}
The LTC^®3731 is a PolyPhase^® synchronous step-down
switching regulator controller that drives all N-channel ex-
ternal power MOSFET stages in a phase-lockable fixed fre-
quency 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 frequency,
improving transient response while operating each control-
ler at an optimal frequency for efficiency and ease of ther-
mal 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. The precision reference supports output voltages from
0.6V to 6V.
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.
, 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.
*Protected by U.S. Patents including 5481178, 5929620, 6177787, 6144194, 6100678,
5408150, 6580258, 6462525, 6304066, 5705919.
TYPICAL APPLICATIO
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^–
TG2
PGOOD
PLLIN
SW2
PLLFLTR
BG2
36k
V_IN
12k
680pF
UVADJ
PGND
SENSE2⁺
SENSE2^–
5k
7.5k
6.04k
I_TH
RUN/SS
0.01µF
SGND
100pF
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
3731fa
1