GENERAL DESCRIPTION

The LT®8641A step-down regulator features Silent

Switcher architecture designed to minimize EMI

emissions while delivering high efficiency at frequencies

up to 3MHz. Assembled in a 3mm × 4mm side wettable

QFN, the monolithic construction 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 LT8641A allows high VIN to low VOUT conversion at

high frequency with a fast minimum top switch on-time

of 35ns. Operation is safe in overload even with a

saturated inductor.

Essential features are included and easy to use: an opendrain

PG pin signals when the output is in regulation.

The SYNC/MODE pin selects between Burst Mode, pulseskipping,

or spread spectrum mode, and also allows

synchronization to an external clock. Soft-start and

tracking functionality are accessed through 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.

FEATURES

 Silent Switcher® Architecture

 Ultralow EMI Emissions

 Spread Spectrum Frequency Modulation

 High Efficiency at High Frequency

 Up to 95 Efficiency at 1MHz, 12VIN to 5VOUT

 Up to 94 Efficiency at 2MHz, 12VIN to 5VOUT

 Wide Input Voltage Range: 3V to 65V

 3.5A Maximum Continuous, 5A Peak Transient

Output

 Ultralow Quiescent Current Burst Mode®

Operation

 2.5μA IQ Regulating 12VIN to 3.3VOUT

 Output Ripple < 10mVP-P

 Fast Minimum Switch On-Time: 35ns

 True 2MHz Operation for 24VIN Systems

 Low Dropout Under All Conditions: 130mV at 1A

 Safely Tolerates Inductor Saturation in Overload

 Adjustable and Synchronizable: 200kHz to 3MHz

 Output Soft-Start and Tracking

 Small 18-Lead 3mm × 4mm Side Wettable QFN with Improved Solder Joint Reliability

 AEC-Q100 Qualified for Automotive Applications

APPLICATIONS

 Automotive and Industrial Supplies

 General Purpose Step-Down