LTC3256 - Wide VIN Range Dual Output 350mA Step-Down Charge Pump with Watchdog Timer

Features

  • Input Voltage Range: 5.5V to 38V
  • Independently Enabled 5V and 3.3V Fixed Outputs
  • 5V Output: 100mA Max
  • 3.3V LDO Output: 250mA Max
  • Multimode Step-Down Charge Pump (2:1, 1:1) with Automatic Mode Switching
  • Low Quiescent Current
    • 20μA with Both Outputs Regulating (No Load)
    • 0.5μA in Shutdown
  • Engineered for Diagnostic Coverage in ISO26262 Systems
  • 1.1V Reference Output for System Diagnostics
  • Power-On Reset and Watchdog Controller with Adjustable Timing
  • Overcurrent Fault Protection on Each Output
  • Overtemperature Protection
  • 150°C Max Operating Junction Temperature
  • Thermally Enhanced 16-Lead MSOP Package

Typical Application

LTC3256 Typical Application
LTC3256 Typical Application

Description

The LTC3256 is a wide input range switched capacitor step-down DC/DC converter that produces two regulated outputs: a 5V output via direct connection to the charge pump output, and a 3.3V output via a low dropout (LDO) linear post-regulator. The device provides up to 350mA of total output current. At 12V VIN and maximum load on both outputs, power dissipation is reduced by over 2W compared to a dual LDO regulator solution.

The LTC3256 maximizes efficiency by running the charge pump in 2:1 mode over as wide an operating range as pos- sible, and automatically switches to 1:1 mode as needed due to V IN and load conditions. Controlled input current and switching slew rates minimize conducted and radiated EMI. An integrated watchdog timer, independent power good outputs and reset input ensure reliable system operation and fault monitoring. A buffered 1.1V reference output enables system self-testing for safety critical applications.

The LTC3256 has numerous safety features including overcurrent fault protection, overtemperature protection and tolerance of 38V input transients. The LTC3256 is available in a thermally enhanced 16-lead MSOP plastic package with exposed pad (MSE16).

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
LTC3256EMSE#PBF MS-16E MSE E 05-08-1667 Yes
LTC3256EMSE#TRPBF MS-16E MSE E 05-08-1667 Yes
LTC3256HMSE#PBF MS-16E MSE H 05-08-1667 Yes
LTC3256HMSE#TRPBF MS-16E MSE H 05-08-1667 Yes
LTC3256IMSE#PBF MS-16E MSE I 05-08-1667 Yes
LTC3256IMSE#TRPBF MS-16E MSE I 05-08-1667 Yes
LTC3256MPMSE#PBF MS-16E MSE MP 05-08-1667 Yes
LTC3256MPMSE#TRPBF MS-16E MSE MP 05-08-1667 Yes


LTC3256 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
LTC3256EMSE#PBF MS-16E E $4.22 $2.95 Yes
LTC3256EMSE#TRPBF MS-16E E $4.28 $3.01 Yes
LTC3256HMSE#PBF MS-16E H $5.29 $3.70 Yes
LTC3256HMSE#TRPBF MS-16E H $5.35 $3.76 Yes
LTC3256IMSE#PBF MS-16E I $4.79 $3.35 Yes
LTC3256IMSE#TRPBF MS-16E I $4.85 $3.41 Yes
LTC3256MPMSE#PBF MS-16E MP $11.36 $7.95 Yes
LTC3256MPMSE#TRPBF MS-16E MP $11.42 $8.01 Yes
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* 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
DC2375A LTC3256 Demo Board | Dual Output Step-Down Charge Pump Plus LDO, 5.5V ≤ VIN ≤ 38V, Vout1 = 5V @ 100mA, Vout2 = 3.3V @ 250mA $100.00
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Click here to view our complete list of demo boards

Applications

  • Automotive ECU/CAN Transceiver Supplies
  • Industrial/Telecom Housekeeping Supplies
  • Low Power 12V to 5V and 3.3V Conversion

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Design Tools

Linear Technology provides a variety of custom design simulation tools and device models to allow even novice designers to quickly and easily evaluate circuits using high performance switching regulators, amplifiers, data converters, filters and more. Please visit our Design Tools page to view and download:

  • LTspice IV - A powerful SPICE simulator, schematic capture and waveform viewer with enhancements and models for easing the simulation of switching regulators
  • LTpowerCAD - A complete power supply selection, synthesis and design tool
  • LTpowerPlay - A development environment supporting Linear Technology's Digital Power System Management (PSM) products
  • PScope & QuikEval - USB-based product demonstration and data acquisition system for use with our ADCs, DACs, and more
  • Linduino - Arduino compatible system for developing and distributing firmware libraries and example code
  • LinearLab Tools - A collection of Matlab and Python programs that provide direct access to Linear Technology’s data converter evaluation boards
  • And More!

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