1

LTC1872B

APPLICATIO S

FEATURES

DESCRIPTIO

Constant Frequency

Current Mode Step-Up

DC/DC Controller in ThinSOT

The LTC

step-up DC/DC controller providing excellent AC and DC

load and line regulation. The device incorporates an accu-

rate undervoltage lockout feature that shuts down the

LTC1872B when the input voltage falls below 2.0V.

The LTC1872B provides a

±2.5% output voltage accuracy

and consumes only 270

µA of quiescent current. In shut-

down, the device draws a mere 8

µA.

High constant operating frequency of 550kHz allows the

use of a small external inductor. The constant frequency

operation is maintained down to very light loads, resulting

in less low frequency noise generation over a wide load

current range.

The LTC1872B is available in a 6-lead low profile (1mm)

ThinSOT package. For a Burst Mode operation enabled

version of the LTC1872B, please refer to the LTC1872 data

sheet.

s

Optical Communications

s

Lithium-Ion-Powered Applications

s

Cellular Telephones

s

Wireless Devices

s

Portable Computers

s

Scanners

s

Burst Mode

Ripple at Light Loads

s

High Efficiency: Over 90%

s

High Output Currents Easily Achieved

s

s

s

Constant Frequency 550kHz Operation

s

Current Mode Operation for Excellent Line and Load

Transient Response

s

Shutdown Mode Draws Only 8

µA Supply Current

s

Low Profile (1mm) ThinSOT

Typical Efficiency vs Load Current*

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

Burst Mode and ThinSOT are trademarks of Linear Technology Corporation.

LTC1872B

147k

422k

80.6k

R1

0.03

Ω

L1

4.7

µH

220pF

C1: TAIYO YUDEN CERAMIC EMK325BJ106MNT

C2: MURATA GRM42-2X5R106K010AL

D1: IR10BQ015

L1: MURATA LQN6C4R7M04

M1: Si2302DS

R1: DALE 0.25W

GND

5

4

6

1872B TA01

1

2

3

NGATE

C1

10

µF

10V

3.3V

5V

1A

C2

4

× 10µF

10V

M1

D1

Figure 1. LTC1872B High Output Current 3.3V to 5V Boost Converter

1

10

100

1000

LOAD CURRENT (mA)

100

95

90

85

80

75

70

65

1872B TA01b

*Output ripple waveforms for the circuit of Figure 1 appear in Figure 2.