LTC3421

10

3421f

OPERATIO

The circuit connected to BURST should be able to sink or

source up to 2mA. Note that Burst Mode operaton is

inhibited during start-up and soft-start.

Mode operation and the synchronous rectifier will be

disabled.

Note that if the load applied during forced Burst Mode

operation exceeds the current that can be supplied, the

output voltage will start to droop and the part will auto-

matically come out of Burst Mode operation and enter fixed

can be supplied in Burst Mode operation is given by:

Simplified Diagram of Automatic Burst Mode Control Circuit

24

TO

MODULATOR

CLAMP

0.5V TO 1V

SLEEP

3421 TA03

ERROR AMP/

SLEEP COMP

±1%

–

+

–

+

9 BURST

0.9V/

1.1V

SSDONE

MODE

1 = Burst Mode

OPERATION

0 = PWM MODE

SSDONE

–4%

UV

1mA

1

FB

I

VV

V

in amps

O MAX

OUT

IN

IN

()

.

•

–

=

+

()

055

2

1

OUTPUT DISCONNECT AND INRUSH LIMITING

The LTC3421 is designed to allow true output disconnect

by eliminating body diode conduction of the internal

volts during shutdown without drawing any current from

the input source. It also allows for inrush current limiting

at turn-on, minimizing surge currents seen by the input

supply. Note that to obtain the advantages of output