LTC1702I 查看數據表（PDF） - Linear Technology

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LTC1702I

Dual 550kHz Synchronous 2-Phase Switching Regulator Controller

Linear Technology 

TEST CIRCUIT

fOSC

MEASURED

5V

10k

VPGOOD1

VFB1

LTC1702

Test Circuit 1

5V

0.1µF

IBOOST1 ICC

VCC

BOOST1

IPVCC

PVCC

BOOST2

+

IBOOST2

100µF

TG1

TG2

BG1

BG2

SW1

CL

CL

IMAX1

SW2

IMAX2

FCB LTC1702

CL

CL

5V

10k

PGOOD1

PGOOD2

FAULT

RUN/SS1

RUN/SS2

2k

2k

COMP1

COMP2

VPGOOD2

VFAULT

FB1

FB2

VFB2

GND PGND

1702 TC

APPLICATIONS INFORMATION

OVERVIEW

The LTC1702 is a dual, step-down (buck), voltage mode

feedback switching regulator controller. It is designed to

be used in a synchronous switching architecture with two

external N-channel MOSFETs per channel. It is intended to

operate from a low voltage input supply (7V maximum)

and provide a high power, high efficiency, precisely regu-

lated output voltage. Several features make it particularly

suited for microprocessor supply regulation. Output regu-

lation is extremely tight, with DC line and load regulation

and initial accuracy better than 1%, and total regulation

including transient response inside of 3% with a properly

designed circuit. The 550kHz switching frequency allows

the use of physically small, low value external components

without compromising performance.

The LTC1702’s internal feedback amplifier is a 25MHz

gain-bandwidth op amp, allowing the use of complex

multipole/zero compensation networks. This allows the

feedback loop to maintain acceptable phase margin at

higher frequencies than traditional switching regulator

controllers allow, improving stability and maximizing tran-

sient response. The 800mV internal reference allows

regulated output voltages as low as 800mV without exter-

nal level shifting amplifiers.

The LTC1702’s synchronous switching logic transitions

automatically into Burst Mode operation, maximizing effi-

ciency with light loads. Onboard power-good and over-

voltage (OV) fault flags indicate when the output is in

regulation or an OV fault has occurred. The OV flag can be

set to latch the device off when an OV fault has occurred,

or to automatically resume operation when the fault is

removed.

The LTC1702 takes a low input voltage and generates two

lower output voltages at very high currents. Its strengths

are small size, unmatched regulation and transient

response and high efficiency. This combination makes it

ideal for providing multiple low voltage logic supplies to

microprocessors or high density ASICs in systems using

a “2-step” regulation architecture, used in portable and

advanced desktop computers.

1702fa

7

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