1

LTC1147-3.3

LTC1147-5/LTC1147L

sn1147 1147fds

High Efficiency Step-Down

Switching Regulator Controllers

Figure 1. High Efficiency Step-Down Converter

APPLICATI

TYPICAL

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

0V = NORMAL

>1.5V = SHUTDOWN

P-CHANNEL

Si4431DY

+

1

µF

L*

50

µH

0.05

Ω

5V/2A

+

100

µF

470pF

3300pF

1k

+

390

µF

D1

MBRD330

LT1147 • F01

GND

PDRIVE

LTC1147-5

SHDN

1000pF

COILTRONICS CTX50-2-MP

KRL SL-1-C1-0R050J

*

**

LOAD CURRENT (A)

0.001

70

90

95

100

0.01

0.1

1

LT1147 • TA01

85

80

75

LTC1147-5 Efficiency

s

Very High Efficiency: Over 95% Possible

s

s

Current Mode Operation for Excellent Line and Load

Transient Response

s

High Efficiency Maintained Over Three Decades of

Output Current

s

Low 160

µA Standby Current at Light Loads

s

s

Short-Circuit Protection

s

Very Low Dropout Operation: 100% Duty Cycle

s

High Efficiency in a Small Amount of Board Space

s

Output Can Be Externally Held High in Shutdown

s

Available in 8-Pin SO Package

The LTC

controllers featuring automatic Burst Mode

maintain high efficiencies at low output currents. These

devices drive an external P-channel power MOSFET at

switching frequencies exceeding 400kHz using a constant

off-time current mode architecture providing constant

ripple current in the inductor.

The operating current level is user-programmable via an

external current sense resistor. Wide input supply range

allows operation from 3.5V* to 14V (16V maximum).

Constant off-time architecture provides low dropout regu-

and resistance of the inductor and current sense resistor.

The LTC1147 series incorporates automatic power saving

Burst Mode operation to reduce switching losses when

load currents drop below the level required for continuous

operation. Standby power is reduced to only 2mW at

operation are typically 0mA to 300mA.

For applications where even higher efficiency is required,

refer to the LTC1148 data sheet and Application Note 54.

Burst Mode is a trademark of Linear Technology Corporation.

*LTC1147L and LTC1147L-3.3 only.

FEATURES

DESCRIPTIO

APPLICATIO S

s

Notebook and Palmtop Computers

s

Portable Instruments

s

Battery-Operated Digital Devices

s

Cellular Telephones

s

DC Power Distribution Systems

s

GPS Systems