Linear Technology LT8641 Offers a Unique Mix of Features

LT8641offers Silent Switcher architecture combined with spread spectrum switching frequency modulation, up to 3MHz switching frequency, synchronous rectification, 3 to 65V input voltage range, 3,5A output current and much more.
This is an archive article published 04/11/2017. Some information may no longer be up to date and in line with the current state. Please contact us in case of interest.

The LT8641 is a monolithic, constant frequency, current mode synchronous (external schottky diode is not necessary) step-down switching regulator. Its 3V to 65V input voltage range makes it ideal for 12V or 24V automotive and industrial applications. It delivers up to 3.5A of continuous output current and peak loads of 5A. Output voltages can be set in 0.81 to 64V range.

LT8641Silent Switcher, when combined with proper PCB layout, provides almost ideal square wave in the switching node almost without ringing, which reduces HF energy that can potentially radiate outside. When combined with spread spectrum frequency modulation, it reduces EM emissions by more than 25dB even with switching frequencies in excess of 2MHz, enabling it to easily pass the automotive CISPR25 class 5 peak and average EM emission limits.

Minimum typical on-time of only 35ns enables 2MHz constant frequency operation from 24V input to 3.3V output, which allows the use of small sized inductor while avoiding critical noise sensitive frequency bands like AM radio band. For even lower EMI, the device can operate below AM band.

Besides 65V absolute maximum input voltage rating in automotive environments, the dropout behavior is also very important. The LT8641 maintains the close to ideal behavior. The device skips its switch-off cycles in dropout and performs only the minimum required off cycles to keep the internal top switch boost stage voltage sustained. LT8641 maintains a minimum dropout voltage of only 130mV at 1A under all conditions, enabling it to supply 3.3V rail even during automotive cold crank.

The device’s Burst Mode keeps quiescent current under 2.5µA. This is the total supply current consumed by the device, output in regulation, with no load. This mode maintains high efficiency at low output currents while keeping output ripple below 10mVP-P.

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  • Silent Switcher® Architecture -Ultralow EM Emissions / Spread Spectrum Frequency Modulation
  • Efficiency Up to 95% at 1MHz, Up to 94% at 2MHz
  • Wide Input Voltage Range: 3V to 65V
  • Ultralow Quiescent Current Burst Mode Operation, 2.5µA IQ Regulating 12VIN to 3.3VOUT, Output Ripple < 10mVP-P
  • Minimum Switch-On Time: 35ns
  • Low Dropout Under All Conditions: 130mV at 1A, 500mV at 3.5A
  • Safely Tolerates Inductor Saturation in Overload
  • Adjustable & Synchronizable frequency: 200kHz to 3MHz
  • Peak Current Mode Operation
  • Internal Compensation
  • Output Soft-Start & Tracking

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