LTC1695

1

FEATURES

APPLICATIO S

DESCRIPTIO

The LTC

tions necessary for a power management microprocessor

to regulate the speed of a 5V brushless DC fan via a 2-wire

the system’s required temperature profile and permits

lower fan power consumption, longer battery run time and

lower acoustical generated noise versus systems that

only provide simple on-off control for the fan.

The LTC1695 incorporates a 180mA low dropout linear

Fan speed is controlled by varying the fan’s terminal

voltage through the output voltage of the LTC1695’s linear

regulator. The LTC1695’s output voltage is programmed

by sending a 6-bit digital code to the LTC1695 DAC via the

SMBus. To eliminate fan start-up problems at lower fan

voltages, users can enable the LTC1695’s boost start

feature that provides the DAC’s full-scale output voltage

for 250ms before decreasing to the programmed output

voltage.

The LTC1695 includes output current limiting and thermal

shutdown as well as status monitors that can be read back

by the microprocessor during fault conditions. The

LTC1695 is available in a 5-lead SOT-23 package.

s

Notebook Computers

s

Spot Cooling

s

Portable Instruments

s

Battery-Powered Systems

s

DC Motor Control

s

White LED Power Supplies

s

Programmable Low Dropout Regulator

s

Control System in a 5-Pin SOT-23 package

s

0.75

Ω PMOS Linear Regulator with 180mA

Output Current Rating

s

0V to 4.922V Output Voltage Range Controlled by a

6-Bit DAC

s

s

250ms Internal Timer Ensures Fan Start-Up

s

Current Limit and Thermal Shutdown

s

Fault Status Indication via SMBus Host Readback

Controller in SOT-23

LTC1695

15

2

3

4

GND

SCL

SDA

+

SYSTEM

CONTROLLER

+

4.7

µF

10

µF

5V DC FAN

SUNON

KDE0502PFB2-8

0.6W, 1.7 CFM

(25 • 25 • 10)mm

3

5V

1695 • TA01

Fan Voltage and Current vs DAC Code

DAC CODE

0

120

100

80

60

40

20

0

6

5

4

3

2

1

0

30

50

1695 • TA02

10

20

40

60

70

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