Features

• Silent Switcher® Architecture
• Ultralow EMI/EMC Emissions
• Spread Spectrum Frequency Modulation
• High Efficiency at High Frequency
• Up to 95% Efficiency at 1MHz
• Up to 94% Efficiency at 2MHz
• Wide Input Voltage Range: 3V to 65V
• 3.5A Maximum Continuous Output,
• 5A Peak Transient Output
• Ultralow Quiescent Current Burst Mode^® Operation
• 2.5μA I_Q Regulating 12V_IN to 3.3V_OUT
• Output Ripple < 10mV_P-P
• Fast Minimum Switch-On Time: 35ns
• Low Dropout Under All Conditions: 130mV at 1A
• Safely Tolerates Inductor Saturation in Overload
• Adjustable and Synchronizable: 200kHz to 3MHz
• Peak Current Mode Operation
• Output Soft-Start and Tracking
• Small 18-Lead 3mm × 4mm QFN

Typical Application

Description

The LT®8641 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 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 10mV_P-P at any load, from zero to full current.

The LT8641 allows high V_IN to low V_OUT 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 open-drain PG pin signals when the output is in regulation. The SYNC/MODE pin selects between Burst Mode, pulse-skipping, or spread spectrum mode, and also allows synchronization to an external clock. 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.