LTC1773

1

1773fb

APPLICATIO S

DESCRIPTIO

FEATURES

TYPICAL APPLICATIO

µµµµµA

Load Transient Response

■

±1.5% Reference Accuracy

The LTC

lator controller that drives external complementary power

MOSFETs using a fixed frequency architecture. The oper-

ating supply range is from 2.65V to 8.5V, making it

suitable for 1- or 2-cell lithium-ion battery powered appli-

cations. Burst Mode

low load currents. 100% duty cycle provides low dropout

operation which extends operating time in battery-oper-

ated systems.

The operating frequency is internally set at 550kHz, allow-

ing the use of small surface mount inductors. For switch-

ing-noise sensitive applications, it can be synchronized up

to 750kHz. Peak current limit is user programmable with

an external high side sense resistor. A SYNC/FCB control

pin guarantees regulation of secondary windings regard-

less of load on the main output by forcing continuous

operation. Burst Mode operation is inhibited during syn-

chronization or when the SYNC/FCB pin is pulled low to

reduce noise and RF interference. Soft-start is provided by

an external capacitor.

Synchronous rectification increases efficiency and elimi-

nates the need for a Schottky diode, saving components

and board space. The LTC1773 comes in a 10-lead MSOP

package.

Synchronous Step-Down

DC/DC Controller

Figure 1. Step-Down Converter

High Efficiency

OUTPUT CURRENT (mA)

100

95

90

85

80

75

70

65

60

55

1

100

1000

5000

1773 F1b

10

L = SUMIDA CDRH6D28-3R0

+

+

30k

220pF

0.1

µF

180

µF

68

µF

L1

3

µH

2.65V TO 8.5V

2.5V

0.025

Ω

1773 F01

LTC1773

RUN/SS

SYNC/FCB

GND

SENSE

–

TG

BG

SW

Si9801DY

80.6k

169k

47pF

Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815.

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology Corporation.