LTC1701(1999) Ver la hoja de datos (PDF) - Linear Technology

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LTC1701
(Rev.:1999)

1MHz Step-Down DC/DC Converter in SOT-23

Linear Technology 

LTC1701

PI FU CTIO S

SW (Pin 1): The Switch Node Connection to the Inductor.

This pin swings from VIN to a Schottky diode (external)

voltage drop below ground. The cathode of the Schottky

diode must be closely connected to this pin.

GND (Pin 2): Ground Pin. Connect to the (–) terminal of

COUT, the Schottky diode and (–) terminal of CIN.

VFB (Pin 3): Receives the feedback voltage from the

external resistive divider across the output. Nominal volt-

age for this pin is 1.25V.

ITH/RUN (Pin 4): Combination of Error Amplifier Compen-

sation Point and Run Control Input. The current compara-

tor threshold increases with this control voltage. Nominal

voltage range for this pin is 1.25V to 2.25V. Forcing this

pin below 0.8V causes the device to be shut down. In

shutdown all functions are disabled.

VIN (Pin 5): Main Supply Pin and the (+) Input to the

Current Comparator. Must be closely decoupled to ground.

Pin Limit Table

PIN

NAME

1

SW

2

GND

3

VFB

4

ITH/RUN

5

VIN

DESCRIPTION

Switch Node

Ground Pin

Output Feedback Pin

Error Amplifier Compensation and RUN Pin

Main Power Supply

NOMINAL (V)

MIN TYP MAX

– 0.3

VIN

0

0

1.25 1.35

0

2.25

2.5

5.5

ABSOLUTE MAX (V)

MIN

MAX

– 0.3

VIN + 0.3

– 0.3

3

– 0.3

3

– 0.3

6

BLOCK DIAGRA

VREF

ITH/RUN

VREF

VFB

+

ITH/REF

CLAMP

–

+

ERROR

AMP

–

VIN

50µA

VIN

1.25V

BANDGAP

REFERENCE

1.5V

SHDN

(1.25V TO 2.25V)

+

ITH

COMP

–

+

OVER

VOLTAGE

1.4V

– COMP

PULSE

STRETCHER

VFB < 0.6V

VREF

(1.25V)

VIN

+

CURRENT

COMP

–

VREF

+

CURRENT

SENSE

AMP –

OFF-TIMER

AND GATE

CONTROL LOGIC

GATE

DRIVER

GND

SW

1701 BD

3

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