LTC3727 查看數據表（PDF） - Linear Technology

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LTC3727

High Efficiency, 2-Phase Synchronous Step-Down Switching Regulators

Linear Technology 

LTC3727/LTC3727-1

High Efficiency, 2-Phase

Synchronous Step-Down Switching Regulators

FEATURES

s Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 14V

s Out-of-Phase Controllers Reduce Required Input

Capacitance and Power Supply Induced Noise

s OPTI-LOOP® Compensation Minimizes COUT

s ±1% Output Voltage Accuracy

s Power Good Output Voltage Monitor

s Phase-Lockable Fixed Frequency 250kHz to 550kHz

s Latched Short-Circuit Shutdown (LTC3727 Only)

s Dual N-Channel MOSFET Synchronous Drive

s Wide VIN Range: 4V to 36V Operation

s Very Low Dropout Operation: 99% Duty Cycle

s Adjustable Soft-Start Current Ramping

s Foldback Output Current Limiting

s Output Overvoltage Protection

s Low Shutdown IQ: 20µA

s Small 28-Lead SSOP Package

s LTC3727-1 Also Available in the 5mm × 5mm QFN

Package

s Selectable Constant Frequency or Burst Mode®

Operation

U

APPLICATIO S

s Telecom Systems

s Automotive Systems

s Battery-Operated Digital Devices

DESCRIPTIO

The LTC®3727/LTC3727-1 are high performance dual

step-down switching regulator controllers that drive all

N-channel synchronous power MOSFET stages. A con-

stant frequency current mode architecture allows phase-

lockable frequency of up to 550kHz. Power loss and noise

due to the ESR of the input capacitors are minimized by

operating the two controller output stages out of phase.

OPTI-LOOP compensation allows the transient response

to be optimized over a wide range of output capacitance and

ESR values. There is a precision 0.8V reference and a power

good output indicator. A wide 4V to 30V (36V maximum)

input supply range encompasses all battery chemistries.

A RUN/SS pin for each controller provides soft-start, and

on the LTC3727GN, optional timed, short-circuit shut-

down. Current foldback limits MOSFET heat dissipation

during short-circuit conditions when overcurrent latchoff

is disabled. Output overvoltage protection circuitry latches

on the bottom MOSFET until VOUT returns to normal. The

FCB mode pin can select among Burst Mode, constant

frequency mode and continuous inductor current mode or

regulate a secondary winding. The LTC3727/LTC3727-1

include a power good output pin that indicates when both

outputs are within 7.5% of their designed set point.

, LTC and LT are registered trademarks of Linear Technology Corporation.

Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation.

TYPICAL APPLICATIO

8µH

0.015Ω

VOUT1

5V

5A

+

47µF

6V

SP

105k

1%

+

4.7µF

M1

0.1µF

M2

1000pF

220pF

20k

1%

15k

VIN PGOOD INTVCC

TG1

TG2

BOOST1

BOOST2

SW1

SW2

LTC3727/

BG1 LTC3727-1 BG2

PLLIN

SENSE1+

PGND

SENSE2+

SENSE1–

SENSE2–

VOSENSE1

VOSENSE2

ITH1

ITH2

RUN/SS1 SGND RUN/SS2

0.1µF

0.1µF

1µF

CERAMIC

M3

0.1µF

M4

VIN

22µF 18V TO 28V

50V

CERAMIC

15µH

1000pF

220pF

15k

280k

1%

20k

1%

0.015Ω

VOUT2

12V

4A

56µF

15V

SP

M1, M2, M3, M4: FDS6680A

Figure 1. High Efficiency Dual 12V/5V Step-Down Converter

1628 F01

3727f

1

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