New Content (2)
Features and Benefits
- Silent Switcher®2 Architecture
- Ultralow EMI Emissions
- Optional Spread Spectrum Modulation
- Two High Voltage Synchronous Buck Regulators
- 3V to 42V Input Voltage Range
- Output Currents Up to 2.5A per Channel
- Channels May Be Connected in Parallel Using a Single Inductor
- Two Low Voltage Synchronous Buck Regulators
- 3V to 8V Input Voltage Range
- Output Currents Up to 4A per Channel
- Channels May Be Connected in Parallel Using a Single Inductor
- 12μA IQ All Channels Active and No-Load
- Flexible Supply Sequencing and Control
- Adjustable and Synchronizable: 350kHz to 3MHz
- Available in 36-Lead LQFN (5mm × 6mm) AEC-Q100 Qualified for Automotive Applications
The LT8685S is a highly flexible, four channel, current mode, monolithic regulator able to power a wide range of automotive and industrial applications while occupying minimal board space.
The LT8685S combines two 42V capable 2.5A buck regulators with two 8V capable 4A buck regulators. The two 42V regulators may be combined to provide up to 5A of output current using a single inductor. Similarly, the two 8V regulators may be combined to provide up to 8A of output current using a single inductor. Individual channel enable, track/soft-start and power good pins provide flexible power supply sequencing and control. The LT8685S features a Silent Switcher 2 architecture, plus selectable spread spectrum mode, to provide ultralow EMI/EMC emissions while delivering high efficiency at high switching frequencies.
The LT8685S incorporates thermal shutdown and individual channel cycle-by-cycle current limit for short circuit protection and robust operation.
- Automotive Systems
- Industrial Controls and 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 EVAL-LT8685S-AZ is a 4-rail power supply featuring the LT8685S, a 42V quad monolithic synchronous step-down silent switcher. The demo circuit is designed for 5V, 3.3V, 1.8V, and 1.2V outputs from a nominal 12V input. The 5V and 3.3V rails are powered from the 12V input, while the 1.8V and 1.2V rails are powered from one of the high voltage buck regulators of 5V or 3.3V. The current capability is 2.5A for the channels 1 and 2. The current ratings for the low voltage channels are 4A.
The two 42V regulators may be combined to provide up to 5A of output current using a single inductor. Similarly, the two 8V regulators may be combined to provide up to 8A of output current using a single inductor.
Individual track/soft-start, current limit, independent enable and power good for each channel simplify the complex design of quad-output power converters. All regulators can be synchronized to a common external clock input or internal oscillator that can be programmed with a single resistor for switching frequency from 350kHz to 3MHz, allowing for optimal system design per specific applications.
The Performance Summary table in the demo manual summarizes the performance of the demo board at room temperature. The circuit can be easily modified for different applications.
The LT8685S data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with the quick start guide for demo circuit EVAL-LT8685S-AZ.
Documentation & Resources
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
Models for the following parts are available in LTspice:
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.View our quality and reliability program and certifications for more information.
|Part Number||Material Declaration||Reliability Data||Pin/Package Drawing||CAD Symbols, Footprints & 3D Models|
|LT8685SRV#PBF||Material Declaration||Reliability Data||36-Lead LQFN Package (5mm x 6mm)|
|LT8685SRV#TRPBF||Material Declaration||Reliability Data||36-Lead LQFN Package (5mm x 6mm)|
|LT8685SRV#WPBF||Material Declaration||Reliability Data||36-Lead LQFN Package (5mm x 6mm)|
|LT8685SRV#WTRPBF||Material Declaration||Reliability Data||36-Lead LQFN Package (5mm x 6mm)|
|Wafer Fabrication Data|
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.