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LGGQ

42V, 4A Synchronous Step-Down Silent Switcher with 2.5µA Quiescent Current

Linear Technology 

LT8614

42V, 4A Synchronous

Step-Down Silent Switcher

with 2.5µA Quiescent Current

Features

Description

n Silent Switcher™ Architecture:

Ultralow EMI/EMC Emissions

n High Efficiency at High Frequency

Up to 96% Efficiency at 1MHz

Up to 94% Efficiency at 2MHz

n Wide Input Voltage Range: 3.4V to 42V

n Ultralow Quiescent Current Burst Mode® Operation:

2.5μA IQ Regulating 12VIN to 3.3VOUT

Output Ripple < 10mVP-P

n Fast Minimum Switch-On Time: 30ns

n Low Dropout Under All Conditions: 200mV at 1A

n Safely Tolerates Inductor Saturation in Overload

n Adjustable and Synchronizable: 200kHz to 3MHz

n Peak Current Mode Operation

n Accurate 1V Enable Pin Threshold

n Internal Compensation

n Output Soft-Start and Tracking

n Small 18-Lead 3mm × 4mm QFN

Applications

n Automotive and Industrial Supplies

n General Purpose Step-Down

n GSM Power Supplies

The LT®8614 step-down regulator features Silent Switcher

architecture designed to minimize EMI/EMC emissions

while delivering high efficiency at frequencies up to 3MHz.

Assembled in a 3mm × 4mm QFN, the monolithic construc-

tion with integrated power switches and inclusion of all

necessary circuitry yields a solution with a minimal PCB

footprint. An ultralow 2.5µA quiescent current—with the

output in full regulation— enables applications requiring

highest efficiency at very small load currents. Transient

response remains excellent and output voltage ripple is

below 10mVP-P at any load, from zero to full current.

The LT8614 allows high VIN to low VOUT conversion at

high frequency with a fast minimum top switch on-time of

30ns. Operation is safe in overload even with a saturated

inductor.

Essential features are included and easy to use: An open-

drain PG pin signals when the output is in regulation. The

SYNC pin allows clock synchronization and choice of Burst

Mode operation or pulse-skipping mode. Soft-start and

tracking functionality is accessed via the TR/SS pin. An

accurate enable threshold can be set using the EN/UV pin

and a resistor at the RT pin programs switch frequency.

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

and Silent Switcher is a trademark of Linear Technology Corporation. All other trademarks are

the property of their respective owners.

Typical Application

VIN

5.8V TO 42V

5V 4A Step-Down Converter

4.7µF

1µF

10nF

1µF

41.2k

VIN1 EN/UV VIN2

GND1

GND2

LT8614

PG

BST

SYNC/MODE SW

TR/SS

BIAS

INTVCC

FB

RT

GND

1µF

0.1µF 4.7µH

VOUT

5V

4A

4.7pF

1M

47µF

243k

fSW = 1MHz

8614 TA01a

12VIN to 5VOUT Efficiency

100

1MHz

95

2MHz

90

85

80

75

70

65

60

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

LOAD CURRENT (A)

8614 TA01b

For more information www.linear.com/LT8614

8614fb

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