LTC3858-1 - Low IQ, Dual 2-Phase Synchronous Step-Down Controller

Features

  • Low Operating IQ: 170μA (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 Burst Mode® Operation at Light Loads
  • Very Low Dropout Operation: 99% Duty Cycle
  • Adjustable Output Voltage Soft-Start
  • Power Good Output Voltage Monitor
  • Output Overvoltage Protection
  • Output Latch-Off Protection During Short Circuit
  • Low Shutdown IQ: 8μA
  • Internal LDO Powers Gate Drive from VIN or EXTVCC
  • No Current Foldback During Start-Up
  • Tiny 4mm × 5mm QFN and Narrow SSOP Packages
Designed for Automotive and Transportation Applications
AEC-Q100 generic family data available for specific packages


Typical Application

LTC3858-1 Typical Application
LTC3858-1 Typical Application

Description

The LTC3858-1 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 input capacitor ESR are minimized by operating the two controller outputs out of phase.

The 170μA no-load quiescent current extends operating life in battery powered systems. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3858-1 features a precision 0.8V reference and a power good output indicator. A wide 4V to 38V input supply range encompasses a wide range of intermediate bus voltages and battery chemistries.

Independent soft-start pins for each controller ramp the output voltages during start-up. The output latch-off feature protects the circuit in short-circuit conditions.

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 LTC3858 data sheet.

 LTC3858LTC3858-1LTC3858-2
Features Adjustable Current Limit, Clock Output, Phase Modulation, 2 PGOOD Outputs Fixed Current Limit, One PGOOD Output Overvoltage protection crowbar and short-circuit latchoff disabled
Package QFN-32 SSOP-28 QFN-32

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
LTC3858EGN-1#PBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3858EGN-1#TRPBF SSOP-28 GN E 05-08-1641 (GN28) Yes
LTC3858EUFD-1#PBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3858EUFD-1#TRPBF 4x5 QFN-28 UFD E 05-08-1712 Yes
LTC3858IGN-1#PBF SSOP-28 GN I 05-08-1641 (GN28) Yes
LTC3858IGN-1#TRPBF SSOP-28 GN I 05-08-1641 (GN28) Yes
LTC3858IUFD-1#PBF 4x5 QFN-28 UFD I 05-08-1712 Yes
LTC3858IUFD-1#TRPBF 4x5 QFN-28 UFD I 05-08-1712 Yes


LTC3858-1 Package Drawing
LTC3858-1 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
LTC3858EGN-1#PBF SSOP-28 E $5.54 $3.88 Yes
LTC3858EGN-1#TRPBF SSOP-28 E $3.94 Yes
LTC3858EUFD-1#PBF 4x5 QFN-28 E $5.71 $4.00 Yes
LTC3858EUFD-1#TRPBF 4x5 QFN-28 E $4.06 Yes
LTC3858IGN-1#PBF SSOP-28 I $5.97 $4.18 Yes
LTC3858IGN-1#TRPBF SSOP-28 I $4.24 Yes
LTC3858IUFD-1#PBF 4x5 QFN-28 I $6.06 $4.24 Yes
LTC3858IUFD-1#TRPBF 4x5 QFN-28 I $4.30 Yes
Buy NowRequest 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-B LTC3858EGN-1 Demo Board | Dual Output, 2-Phase, 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

Please contact your local sales representative for more information regarding reliability reports and AEC-Q100 data 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
LTC3858IGN-1#PBF SSOP-28 I $5.97 $4.18 Yes
LTC3858IGN-1#TRPBF SSOP-28 I $4.24 Yes
Buy NowRequest 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 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

To launch a ready to run LTspice demonstration circuit for this part:

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

To explore other ready to run LTspice demonstration circuits, please visit our Demo Circuits Collection.

Models for the following parts are available in LTspice:
LTC3858
LTC3858-1
LTC3858-2

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:
LTC3858
LTC3858 Parallel
LTC3858-1
LTC3858-1 Parallel
LTC3858-2
LTC3858-2 Parallel

Technical Support