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