LTC3731H_15 Datasheet, PDF (1/34 Pages) Linear Technology – 3-Phase, 600kHz, Synchronous Buck Switching Regulator Controller

LTC3731H
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 _{±2% VREF Accuracy Over Temperature Up to 140°C}
n _{Reduced Power Supply Induced Noise}
n _{±10% Power Good Output Indicator}
n _{225kHz to 680kHz 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 36-Pin Narrow (0.209") SSOP and}
5mm × 5mm QFN Packages
Applications
n _{Automotive and Industrial Power Supplies}
n _{High Output Current DC/DC Power Supplies}
The LTC^®3731H 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 LTC3731H is rated for operation
up to 140°C junction temperature. The 3-phase controller
drives its output stages with 120° phase separation at
frequencies up to 680kHz 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 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.
The precision reference supports output voltages from
0.6V to 6V. Current foldback provides protection for the
external MOSFETs under short-circuit or overload condi-
tions. Please refer to the LTC3731 data sheet for 0°C to
70°C and –40°C to 85°C rated versions.
L, LT, LTC, LTM, Linear Technology, the Linear logo, Burst Mode, OPTI-LOOP and PolyPhase
are registered trademarks 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,
6304066, 5705919.
Typical Application
V_CC
4.5V TO 7V
10µF
0.1µF
SW3 SW2 SW1
POWER GOOD INDICATOR
OPTIONAL SYNC IN
V_CC
TG1
LTC3731H _SW1
BOOST1
BOOST2
BG1
BOOST3
SENSE1⁺
SENSE1^–
TG2
PGOOD
PLLIN
SW2
PLLFLTR
BG2
0.8µH
0.003Ω
V_IN
+
5V TO 28V
22µF
35V
V_IN
0.8µH
0.003Ω
V_OUT
1.35V
55A
36k
V_IN
12k
5k
UVADJ
680pF
I_TH
RUN/SS
0.01µF
SGND
EAIN
100pF
7.5k
6.04k
PGND
SENSE2⁺
SENSE2^–
TG3
SW3
BG3
SENSE3⁺
SENSE3^–
V_IN
0.8µH
0.003Ω
+ C_OUT
470µF
4V
3731H F01
Figure 1. High Current Triple Phase Step-Down Converter
Efficiency vs I_OUT
100
90 ^VFCB ^{= OPEN}
80 ^VFCB ^{= 5V}
70
V_FCB = 0V
60
50
40
30
20
10
0
0.1
V_IN = 8V
V_OUT = 1.5V
1
10
LOAD CURRENT (A)
100
3731H F01b
3731Hfb