LT3668

1

3668fa

For more information www.linear.com/LT3668

TYPICAL APPLICATION

FEATURES

DESCRIPTION

40V 400mA Step-Down

Switching Regulator with Dual

Fault Protected Tracking LDOs

TheLT®3668isamonolithictriplepowersupplycomposed

of a 400mA buck switching regulator and two 200mA low

dropout linear tracking regulators (LDOs).This provides a

complete and robust power solution for applications that

require the power supply of a sensor to tightly track the

power supply of a measurement ASIC.

Each tracking LDO supplies 200mA of output current with

a typical dropout voltage of 340mV, and each LDO has an

accurate resistor programmable current limit.

Internal protection circuitry includes reverse-battery

protection, current limiting, thermal limiting and reverse

current protection.

The buck regulator includes a high efficiency switch, a

boost diode, and the necessary oscillator, control and

logic circuitry. Current mode topology is used for fast

transient response and good loop stability. Low ripple

Burst Mode operation maintains high efficiency at low

output currents while keeping output ripple below 15mV

in a typical application.

The LT3668 is available in a thermally-enhanced 16-lead

MSOPpackagewithexposedpadforlowthermalresistance.

No-Load Supply Current

APPLICATIONS

n

Dual Low Dropout Linear Tracking Regulators

n

200mA Outputs with Programmable Current Limits

n

1.6V to 45V Input Range

n

Fault Protected to ±45V

n

Triple Output Supply from a Single Input Requires

Only One Inductor

n

n

Buck Regulator:

n

n

400mA Output with Internal Power Switch

n

4.3V to 40V Input Operation Range (60V Max)

n

Adjustable 250kHz to 2.2MHz Switching Frequency

n

Power Good Indicator

n

Available in a Thermally-Enhanced 16-Lead

MSOP Package

n

Fault-Protected Sensor Supply

n

Automotive and Industrial Supplies

n

Power for Portable Instrumentation

L

, LT, LTC, LTM, Burst Mode, Linear Technology and the Linear logo are registered trademarks

of Linear Technology Corporation. All other trademarks are the property of their respective

owners.

INPUT VOLTAGE (V)

5

0

10

30

40

50

100

70

15

25

30

3668 TA01b

20

80

90

60

10

20

35

3668 TA01a

EN2/ILIM2

EN3/ILIM3

GND

5V

150mA

10µF

10µF

IN1

LT3668

BOOST

SW

DA

IN3/BD

IN2

FB1

ON OFF

EN

PG

RT

OUT2

OUT3

ADJ3

ADJ2

4.7µF

0.22µF

22pF

27µH

232k

6V

100mA

931k

294k

174k

f = 600kHz

7V TO 40V

TRANSIENT

TO 60V

5V

150mA

(FOLLOWS

OUT3)

22µF