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LT8640/LT8640-1 - 42V, 5A Synchronous Step-Down Silent Switcher with 2.5μA Quiescent Current

The LT®8640/LT8640-1 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 10mVP-P at any load, from zero to full current.

The LT8640/LT8640-1 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 operation, spread spectrum mode, synchronization to an external clock, and either pulse-skipping (LT8640) or forced continuous mode (LT8640-1). 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.

Features Silent Switcher® Architecture Ultralow EMI/EMC Emissions Spread Spectrum Frequency Modulation High Efficiency at High Frequency Up to 96% Efficiency at 1MHz Up to 95% Efficiency at 2MHz Wide Input Voltage Range: 3.4V to 42V 5A Maximum Continuous Output, 7A 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 Low Dropout Under All Conditions: 100mV at 1A Forced Continuous Mode (LT8640-1 Only) 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

Applications Automotive and Industrial Supplies General Purpose Step-Down GSM Power Supplies Packaging

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