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LT3437

3437fc

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Industrial Power Systems

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Powered Ethernet

High Voltage 500mA, 200kHz

Step-Down Switching Regulator

with 100

µA Quiescent Current

µA Quiescent Current**

Ω On-Resistance

Full Duty Cycle Range*

The LT

regulator that accepts input voltages up to 80V. A high

efficiency 500mA, 0.8

Ωswitchisincludedonthediealong

with all the necessary oscillator, control and logic cir-

cuitry. Current mode topology is used for fast transient

response and good loop stability.

Innovative design techniques along with a new high volt-

age process achieve high efficiency over a wide input

range. Efficiency is maintained over a wide output current

range by employing Burst Mode operation at low currents,

utilizing the output to bias the internal circuitry, and by

using a supply boost capacitor to fully saturate the power

switch. Burst Mode operation can be defeated by a logic

high signal on the SYNC pin which results in lower light

load ripple at the expense of light load efficiency. Patented

circuitry maintains peak switch current over the full duty

cycle range.* Shutdown reduces input supply current to

less than 1

µA. External synchronization can be imple-

mented by driving the SYNC pin with logic-level inputs. A

controlled output voltage ramp (soft-start).

The LT3437 is available in a low profile (0.75mm) 3mm

×

3mm 10-pin DFN package or a 16-Pin TSSOP Package,

both with exposed pad leadframes for low thermal

resistance.

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

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

is a registered trademark of Linear Technology Corporation. All other trademarks are the

property of their respective owners. *Protected by U.S. Patents, including 6498466.

**See Burst Mode Operation section for conditions.

SHDN

BOOST

LT3437

2.2

µF

100V

CER

330pF

0.1

µF

0.1

µF

100

µH

BAS21

SYNC

GND

100

µF

6.3V

TANT

3.3V

400mA

4.5V TO 80V*

10MQ100N

1500pF

25k

165k

100k

3437 TA01

27pF

SW

FB

*FOR INPUT VOLTAGES ABOVE 60V RESTRICTIONS APPLY

14V to 3.3V Step-Down Converter with

100

µA No Load Quiescent Current

Supply Current vs Input Voltage

INPUT VOLTAGE (V)

0

0

40

100

10

20

30

40

3437 TA02

50

200

20

60

80

120

140

160

180

80

60

70

Input Voltage

Transient Response

LOAD DUMP

COLD CRANK

20V/DIV

20mV/DIV

AC COUPLED

0V

3437 TA03

50ms/DIV