3728L1 データシートの表示（PDF） - Linear Technology

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3728L1

Dual, 550kHz, 2-Phase Synchronous Regulator

Linear Technology 

FEATURES

n Dual, 180° Phased Controllers Reduce Required

Input Capacitance and Power Supply Induced Noise

n OPTI-LOOP® Compensation Minimizes COUT

n ±1.5% Output Voltage Accuracy

n Power Good Output Voltage Indicator

n Phase-Lockable Fixed Frequency 250kHz to 550kHz

n Over Current Latchoff Disabled

n Wide VIN Range: 4.5V to 28V (35V for LTC3728LI-1)

Operation

n Very Low Dropout Operation: 99% Duty Cycle

n Adjustable Soft-Start Current Ramping

n Foldback Output Current Limiting

n Output Overvoltage Protection

n Low Shutdown IQ: 20μA

n 5V and 3.3V Standby Regulators

n 3 Selectable Operating Modes: Constant Frequency,

Burst Mode® Operation and PWM

n 5mm × 5mm QFN and 28-Lead Narrow SSOP

Packages

APPLICATIONS

n Notebook and Palmtop Computers

n Telecom Systems

n Portable Instruments

n Battery-Operated Digital Devices

n DC Power Distribution Systems

LTC3728L-1

Dual, 550kHz, 2-Phase

Synchronous Regulator

DESCRIPTION

The LTC®3728L-1 is a dual high performance step-down

switching regulator controller that drives all N-channel

synchronous power MOSFET stages. A constant 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. The LTC3728L-1

is identical to the LTC3728L except that the LTC3728L-1

lacks the over current latchoff feature.

OPTI-LOOP compensation allows the transient response to

be optimized over a wide range of output capacitance and

ESR values. The precision 0.8V reference and power good

output indicator are compatible with future microproces-

sor generations, and a wide 4.5V to 28V (30V maximum/

35V for LTC3728LI-1) input supply range encompasses

all battery chemistries.

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

Current foldback limits MOSFET dissipation during short-

circuit conditions. The FCB mode pin can select among

Burst Mode operation, constant frequency mode and

continuous inductor current mode or regulate a secondary

winding. The LTC3728L-1 includes a power good output

pin that indicates when both outputs are within 7.5% of

their designed set point.

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

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

All other trademarks are the property of their respective owners.

Protected by U.S. Patents including 5929620, 6177787, 6144199, 5471178, 5994885, 6100678.

TYPICAL APPLICATION

M1

L1

3.2μH

+

4.7μF

D3

VIN PGOOD INTVCC

D4

TG1

TG2

CB1, 0.1μF

fIN

500kHz

BOOST1

BOOST2

SW1

SW2

LTC3728L-1

BG1

BG2

PLLIN

PGND

CB2, 0.1μF

1μF

CERAMIC

CIN

22μF

VIN

5.2V TO 28V

M2

50V

CERAMIC

L2

3.2μH

RSENSE1

0.01Ω

VOUT1

5V

R2

5A +

COUT1

47μF

105k

1%

6V

SP

R1

20k

1%

1000pF

CC1

220pF

RC1

15k

SENSE1+

SENSE2+

SENSE1–

SENSE2–

VOSENSE1

ITH1

VOSENSE2

ITH2

RUN/SS1 SGND RUN/SS2

CSS1

0.1μF

CSS2

0.1μF

1000pF

CC2

220pF

RC2

15k

RSENSE2

0.01Ω

R4

63.4k

R3

20k

1%

1%

COUT

56μF

6V

SP

VOUT2

3.3V

5A

M1, M2: FDS6982S

3728l1 F01

Figure 1. High Efficiency Dual 5V/3.3V Step-Down Converter

3728l1fc

1

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