LTC1702AIGN datasheet(7/36 Pages) LINER

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LTC1702A

1702afa

TEST CIRCUIT

Test Circuit 1

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 LTC1702A’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 LTC1702A takes a low input voltage and generates

two lower output voltages at very high currents. Its

strengths are small size, unmatched regulation and tran-

sient 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 common

in portable and advanced desktop computers.

OVERVIEW

The LTC1702A 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 LTC1702A’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

APPLICATIONS INFORMATION

VCC

10k

BOOST1

TG1

BG1

SW1

IMAX1

FCB

PGOOD1

RUN/SS1

COMP1

FB1

LTC1702A

BOOST2

TG2

BG2

SW2

IMAX2

PGOOD2

FAULT

RUN/SS2

COMP2

FB2

0.1

µF

100

µF

VPGOOD1

VFB1

VFB2

VPGOOD2

VFAULT

IBOOST1

ICC

IPVCC

IBOOST2

fOSC

MEASURED

1702A TC

PVCC

GND

PGND

10k

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