3

LTC1701

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

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

external resistive divider across the output. Nominal volt-

age for this pin is 1.25V.

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.

Current Comparator. Must be closely decoupled to ground.

PI FU CTIO S

BLOCK DIAGRA

–

+

1.25V

BANDGAP

REFERENCE

CLAMP

SHDN

50

µA

1.4V

1.5V

(1.25V)

–

+

OVER

VOLTAGE

COMP

–

+

COMP

–

+

ERROR

AMP

(1.25V TO 2.25V)

–

+

CURRENT

COMP

–

+

CURRENT

SENSE

AMP

SW

GND

1701 BD

OFF-TIMER

AND GATE

CONTROL LOGIC

GATE

DRIVER

PULSE

STRETCHER

Pin Limit Table

NOMINAL (V)

ABSOLUTE MAX (V)

PIN

NAME

DESCRIPTION

MIN

TYP

MAX

MIN

MAX

1

SW

Switch Node

– 0.3

– 0.3

2

GND

Ground Pin

0

Output Feedback Pin

0

1.25

1.35

– 0.3

3

Error Amplifier Compensation and RUN Pin

0

2.25

– 0.3

3

Main Power Supply

2.5

5.5

– 0.3

6