Features and Benefits
Silent Switcher® 2 Architecture
- Ultralow EMI Emissions on Any PCB
- Eliminates PCB Layout Sensitivity
- Internal Bypass Capacitors Reduce Radiated EMI
- Optional Spread Spectrum 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: 3.4V to 65V
- Ultralow Quiescent Current Burst Mode Operation
- 2.5μA IQ Regulating 12VIN to 3.3VOUT (LT8645S)
- Output Ripple < 10mVP-P
- External Compensation: Fast Transient Response and Current Sharing (LT8646S)
- Fast Minimum Switch On-Time: 40ns
- Low Dropout Under All Conditions: 60mV at 1A
- Adjustable and Synchronizable: 200kHz to 2.2MHz
- Peak Current Mode Operation
- Output Soft-Start and Tracking
- Small 32-Lead 6mm × 4mm LQFN Package
- AEC-Q100 Qualified for Automotive Applications
The LT8645S/LT8646S synchronous step-down regulator features second generation Silent Switcher architecture designed to minimize EMI emissions while delivering high efficiency at high switching frequencies. This includes the integration of bypass capacitors to optimize all the fast current loops inside and make it easy to achieve advertised EMI performance by eliminating layout sensitivity.
The fast, clean, low-overshoot switching edges enable high efficiency operation even at high switching frequencies, leading to a small overall solution size. Peak current mode control with a 40ns minimum on-time allows high step-down ratios even at high switching frequencies. The LT8646S has external compensation to enable current sharing and fast transient response at high switching frequencies.
Burst Mode® operation enables ultralow standby current consumption, pulse-skipping mode allows full switching frequency at lower output loads, or spread spectrum operation can further reduce EMI emissions.
- Automotive and Industrial Supplies
- General Purpose Step-Down
- GSM Power Supplies
Product Lifecycle Recommended for New Designs
This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
Evaluation Kits (1)
Demonstration circuit 2468A is a 65V, 8A micropower synchronous step-down second generation Silent Switcher® with spread spectrum frequency modulation featuring the LT8645S. The demo board is designed for 5V output from a 5.6V to 65V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The LT8645S is a compact, ultralow emission, high efficiency, and high speed synchronous monolithic step-down switching regulator. The integrated bypass capacitors optimize all the fast current loops and make it easier to minimize EMI/EMC emissions by reducing layout sensitivity. Selectable spread spectrum mode can further improve EMI/EMC performance. Ultralow quiescent current in Burst Mode® operation achieves high efficiency at very light loads. Fast minimum on-time of 40ns enables high VIN to low VOUT conversion at high frequency.
Documentation & Resources
R585 Reliability Data4/13/2020
DC2468A - Demo Manual5/17/2017
Tools & Simulations
LTpowerCAD® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.
To open the project file for this circuit:
Step 1: Download and install LTpowerCAD on your computer.
Step 2: Click on the link(s) in the section below to download part-specific project files.
Step 3: If the project file doesn't run, right-click the link and select "Save Target As." Then start the LTpowerCAD tool and open the project file by selecing "Open Project" from the "File" menu.
LTpowerCAD Project Files
Design tools for the following parts are available in LTpowerCAD:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.