LTC1707IS8 查看數據表（PDF） - Linear Technology

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LTC1707IS8

High Efficiency Monolithic Synchronous Step-Down Switching Regulator

Linear Technology 

LTC1707

PI FU CTIO S

ITH (Pin 1): Error Amplifier Compensation Point. The

current comparator threshold increases with this control

voltage. Nominal voltage range for this pin is 0V to 1.2V.

RUN/SS (Pin 2): Combination of Soft-Start and Run

Control Inputs. A capacitor to ground at this pin sets the

ramp time to full current output. The time is approximately

0.5s/µF. Forcing this pin below 0.4V shuts down the

LTC1707.

VFB (Pin 3): Feedback Pin. Receives the feedback voltage

from an external resistive divider across the output.

GND (Pin 4): Ground Pin.

SW (Pin 5): Switch Node Connection to Inductor. This pin

connects to the drains of the internal main and synchro-

nous power MOSFET switches.

VIN (Pin 6): Main Supply Pin. Must be closely decoupled

to GND, Pin 4.

SYNC/MODE (Pin 7): This pin performs two functions:

1) synchronize with an external clock and 2) select be-

tween two modes of low load current operation. To

synchronize with an external clock, apply a TTL/CMOS

compatible clock with a frequency between 385kHz and

550kHz. To select Burst Mode operation, float the pin or

tie it to VIN. Grounding Pin 7 forces pulse skipping mode

operation.

VREF (Pin 8): The Output of a 1.19V ±1% Precision

Reference. May be loaded up to 100µA and is stable with

up to 2000pF load capacitance.

W

FU CTIO AL DIAGRA

BURST

Y = “0” ONLY WHEN X IS A CONSTANT “1”

DEFEAT Y

VIN

X

1.5µA

VIN

VIN

SYNC/MODE

SLOPE

7

COMP

OSC

0.4V

0.6V –

VFB

3

+

VREF

VIN

8

1.19V

REF

UVLO

TRIP = 2.7V

SHUTDOWN

FREQ

SHIFT

0.8V

2.25µA

VIN

RUN/SS 2

+

EA

–

ITH 1

RUN/SOFT

START

0.86V

+

OVDET

–

0.12V

– EN

SLEEP

+

BURST

–+

ICOMP

SQ

RQ

SWITCHING

LOGIC

AND

BLANKING

CIRCUIT

ANTI-

SHOOT-THRU

IRCMP

6 VIN

6Ω

5 SW

4 GND

1707 BD

5

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