1

LTC1878

s

High Efficiency: Up to 95%

s

Very Low Quiescent Current: Only 10

During Operation

s

s

2.65V to 6V Input Voltage Range

s

550kHz Constant Frequency Operation

s

Synchronizable from 400kHz to 700kHz

s

Selectable Burst Mode

Pulse Skipping Mode

s

No Schottky Diode Required

s

Low Dropout Operation: 100% Duty Cycle

s

0.8V Reference Allows Low Output Voltages

s

Shutdown Mode Draws < 1

µA Supply Current

s

±2% Output Voltage Accuracy

s

Current Mode Control for Excellent Line and

Load Transient Response

s

Overcurrent and Overtemperature Protected

s

Available in 8-Lead MSOP Package

The LTC

nous buck regulator using a constant frequency, current

mode architecture. Supply current during operation is

only 10

µA and drops to < 1µA in shutdown. The 2.65V to

6V input voltage range makes the LTC1878 ideally suited

for single Li-Ion battery-powered applications. 100% duty

cycle provides low dropout operation, extending battery

life in portable systems.

Switching frequency is internally set at 550kHz, allowing

the use of small surface mount inductors and capacitors.

For noise sensitive applications the LTC1878 can be

externally synchronized from 400kHz to 700kHz. Burst

Mode operation is inhibited during synchronization or

when the SYNC/MODE pin is pulled low, preventing low

frequency ripple from interfering with audio circuitry.

The internal synchronous switch increases efficiency and

eliminates the need for an external Schottky diode. Low

output voltages are easily supported with the 0.8V feed-

back reference voltage. The LTC1878 is available in a

space saving 8-lead MSOP package.

For higher input voltage (12V abs max) applications, refer

to the LTC1877 data sheet.

s

Cellular Telephones

s

Wireless Modems

s

Personal Information Appliances

s

Portable Instruments

s

Distributed Power Systems

s

Battery-Powered Equipment

High Efficiency Step-Down Converter

High Efficiency

Monolithic Synchronous

Step-Down Regulator

May 2000

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

Burst Mode is a trademark of Linear Technology Corporation.

Efficiency vs Output Load Current

47

µF***

7

6

1

2

5

3

4

SW

LTC1878

GND

10

µH*

22

µF**

CER

220pF

†

3.3V

*

**

***

†

TOKO D62CB A920CY-100M

TAIYO-YUDEN CERAMIC JMK325BJ226MM

SANYO POSCAP 6TPA47M

887k

20pF

280k

1878 TA01

SYNC

RUN

2.65V

TO 6V

+

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

Final Electrical Specifications

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

OUTPUT CURRENT (mA)

80

75

85

90

95

100

0.1

10

100

1000

1878 TA02

70

1

Burst Mode OPERATION

L = 10

µH