Features and Benefits
- Low Operating IQ: 50μA (One Channel On)
- Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
- Wide VIN Range: 4V to 38V
- RSENSE or DCR Current Sensing
- Out-of-Phase Controllers Reduce Required Input Capacitance and Power Supply Induced Noise
- OPTI-LOOP® Compensation Minimizes COUT
- Phase-Lockable Frequency (75kHz-850kHz)
- Programmable Fixed Frequency (50kHz-900kHz)
- Selectable Continuous, Pulse-Skipping or Low Ripple Burst Mode® Operation at Light Loads
- Very Low Dropout Operation: 99% Duty Cycle
- Adjustable Output Voltage Soft-Start or Tracking
- Power Good Output Voltage Monitor
- Output Overvoltage Protection
- Low Shutdown IQ: <8μA
- Internal LDO Powers Gate Drive from VIN or EXTVCC
- No Current Foldback During Start-Up
- Narrow SSOP Package
The LTC3857-1 is a high performance dual step-down switching regulator controller that drives all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows a phase-lockable frequency of up to 850kHz. Power loss and noise due to the ESR of the input capacitor ESR are minimized by operating the two controller output stages out of phase.
The 50μA no-load quiescent current extends operating life in battery-powered systems. The LTC3857-1 features a precision 0.8V reference and a power good output indicator. wide 4V to 38V input supply range encompasses a wide range of intermediate bus voltages and battery chemistries.
Independent TRACK/SS pins for each controller ramp the output voltages during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions. The PLLIN/MODE pin selects among Burst Mode operation, pulse-skipping mode, or continuous inductor current mode at light loads.
For a leadless 32-pin QFN package with the additional features of adjustable current limit, clock out, phase modulation and two PGOOD outputs, see the LTC3857 data sheet.
|Features||Adjustable Current Limit, Clock Output, Phase Modulation, 2 PGOOD Outputs||Fixed Current Limit, One PGOOD Output|
- Automotive Always-On Systems
- Battery Operated Digital Devices
- Distributed DC Power Systems
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 1352A is a low quiescent current, dual output 2-phase, synchronous buck converter demo board featuring the LTC3857EGN-1 or LTC3858EGN-1. It features a 4.5V to 36V input voltage range and provides 3.3V / 5A and 8.5V / 3A outputs. Two versions of the board are available. The DC-1352A-A is for the LTC3857EGN-1, which offers lower quiescent current and smaller burst mode ripple, while the DC1352A-B is for the LTC3858EGN-1 which offers latch-off protection and increased burst mode efficiency.
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.
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.
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.
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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.