42V, 6A Synchronous Step-Down Silent Switcher 2 with 2.5μA Quiescent Current
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Features and Benefits
- Silent Switcher® 2 Architecture
- Ultralow EMI/EMC 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
- 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
The LT8645S synchronous step-down regulator features second generation Silent Switcher architecture designed to minimize EMI/EMC 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. This performance makes the LT8645S ideal for noise sensitive applications and environments.
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.
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/EMC emissions. Soft-start and tracking functionality is accessed via the TR/SS pin, and an accurate input voltage UVLO threshold can be set using the EN/UV pin. A CLKOUT pin enables synchronizing other regulators to the LT8645S.
- Automotive and Industrial Supplies
- General Purpose Step-Down
- GSM Power Supplies
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
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.
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.
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
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.