LINEAR TECHNOLOGY LTC1872 User's Manual

LTC1872

Constant Frequency Current Mode Step-Up DC/DC Controller in SOT-23

FEATURES DESCRIPTIO High Efficiency: Over 90% The LTC®1872 is a constant frequency current mode step- High Output Currents Easily Achieved up DC/DC controller providing excellent AC and DC load Wide VIN Range: 2.5V to 9.8V and line regulation. The device incorporates an accurate VOUT Limited Only by External Components undervoltage lockout feature that shuts down the LTC1872 Constant Frequency 550k Hz Operation when the input voltage falls below 2.0V. Burst Mode TM Operation at Light Load

The LTC1872 boasts a ±2.5% output voltage accuracy and

Current Mode Operation for Excellent Line and Load

consumes only 270µA of quiescent current. For applica-

Transient Response

tions where efficiency is a prime consideration, the LTC1872

Low Quiescent Current: 270µA

is configured for Burst Mode operation, which enhances

Shutdown Mode Draws Only 8µA Supply Current

efficiency at low output current.

±2.5% Reference Accuracy

Tiny 6-Lead SOT-23 Package In shutdown, the device draws a mere 8µA. The high 550k Hz constant operating frequency allows the use of a small external inductor.

EF FI CI EN CY

APPLICATIO S

The LTC1872 is available in a small footprint 6-lead

Lithium-Ion-Powered Applications SOT-23.■ Cellular Telephones

, LTC and LT are registered trademarks of Linear Technology Corporation. Wireless Modems Burst Mode is a trademark of Linear Technology Corporation.

Portable Computers Scanners

TYPICAL APPLICATION

Efficiency vs Load Current

R1 C1 0.03Ω 10µF 10V VIN = 3.3V

147k VOUT = 5V

ITH/RUN VIN

220p F LTC1872

VOUT 5V

GND SENSE–

80.6k 1AC2

VFB NGATE M1 D1 2× 22µF

C1: TAIYO YUDEN CERAMIC EMK325BJ106MNT C2: MURATA GRM42-2X5R226K6.3 D1: IR10BQ015 L1: MURATA LQN6C4R7M04 M1: IRLMS2002

R1: DALE 0.25W 1872 TA01

LOAD CURRENT (m A)

Figure 1. LTC1872 High Output Current 3.3V to 5V Boost Converter 1872 TA01b