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