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LTC4364 - Surge Stopper with Ideal Diode

LTC3857-1 - Low IQ, Dual, 2-Phase Synchronous Step-Down Controller

Features

  • 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
Designed for Automotive and Transportation Applications
AEC-Q100 data available for specific packages

Typical Application

LTC3857-1 Typical Application
LTC3857-1 Typical Application

Description

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.

 LTC3857LTC3857-1
Features Adjustable Current Limit, Clock Output, Phase Modulation, 2 PGOOD Outputs Fixed Current Limit, One PGOOD Output
Package QFN-32 SSOP-28

Packaging

CAD Symbols and Footprints: The downloadable Zip file below contains the schematic symbol and PCB footprints.

For complete and up to date package information and drawings, please refer to our packaging page

Part Number Package Code Temp Package
Drawing		 RoHS
LTC3857EGN-1#PBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3857EGN-1#TRPBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3857IGN-1#PBF SSOP-28 GN I 05-08-1641 (GN28) Yes
LTC3857IGN-1#TRPBF SSOP-28 GN I 05-08-1641 (GN28) Yes


LTC3857-1 Package Drawing

Order Info

  • Part numbers ending in PBF are lead free. Solder plated terminal finish (SnPb) versions are non-standard and special terms and conditions and pricing applies if available. Please contact LTC marketing for information.
  • Part numbers containing TR or TRM are shipped in tape and reel or 500 unit mini tape and reel, respectively
  • Please refer to our general ordering information or the product datasheet for more details

Package Variations and Pricing

Part Number Package Temp Price
(1-99)		 Price
(1k)*		 RoHS
LTC3857EGN-1#PBF SSOP-28 E $5.54 $3.88 Yes
LTC3857EGN-1#TRPBF SSOP-28 E $3.94 Yes
LTC3857IGN-1#PBF SSOP-28 I $5.97 $4.18 Yes
LTC3857IGN-1#TRPBF SSOP-28 I $4.24 Yes
Buy Now • Request Samples
* 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 Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC1352A-A LTC3857EGN-1 Demo Board | Dual Output, 2-Phase, Low Iq, 4.5V ≤ VIN ≤ 36V, Vout1 = 3.3V @ 5A, Vout2 = 8.5V @ 3A $175.00
Buy Now
Click here to view our complete list of demo boards

Designed for Automotive and Transportation Applications

AEC-Q100 data is available for these specific part numbers. Please contact your local sales representative for more information regarding reliability reports or to inquire about parts that are not included. For more information, view our Automotive and Transportation page

Part Number Package Temp Price
(1-99)		 Price
(1k)*		 RoHS
LTC3857IGN-1#PBF SSOP-28 I $5.97 $4.18 Yes
LTC3857IGN-1#TRPBF SSOP-28 I $4.24 Yes
Buy Now • Request Samples
* 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 Linear Technology sales office or authorized distributor.

Applications

  • Automotive Always-On Systems
  • Battery Operated Digital Devices
  • Distributed DC Power Systems

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Design Tools

LTspice

LTspice® software is a powerful, fast and free simulation tool, schematic capture and waveform viewer with enhancements and models for improving the simulation of switching regulators. Click here to download LTspice

Models for the following parts are available in LTspice:
LTC3857
LTC3857-1

LTpowerCAD

The LTpowerCAD design tool is a complete power supply design tool program that can significantly ease the tasks of power supply design. It guides users to a solution, selects power stage components, provides detailed power efficiency, shows quick loop bode plot stability and load transient analysis, and can export a final design to LTspice for simulation. Click here to download LTpowerCAD

To open the project file for this circuit:

  • Step 1: If you have not installed LTpowerCAD on this computer, download and install LTpowerCAD
  • Step 2: Once LTpowerCAD is installed, click on the link(s) below to open the project file
  • Step 3: If LTpowerCAD does not automatically open after clicking the link above, you can open the project file by right clicking on the link and selecting "Save Target As." After saving the file to your computer, start LTpowerCAD and open the project file by selecting 'Open Project' from the 'File' menu

Design tools for the following parts are available in LTpowerCAD:
LTC3857
LTC3857 Parallel
LTC3857-1
LTC3857-1 Parallel

Technical Support