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 from Linear Technology, now part of Analog Devices, is a highly integrated, high voltage low noise dual output power supply, which takes a single positive input and generates 5V and 3.3V step-down supplies with high efficiency and no inductors. The device features a wide 5.5V to 38V input voltage range and includes independently enabled dual outputs: a 5V 100mA supply, and a 250mA 3.3V low-dropout (LDO) regulator, for a total of 350mA available output current.

This combination of regulators offers much lower power dissipation than a dual-LDO solution. For example at 12V VIN and maximum load on both outputs, power dissipation is decreased by over 2W with the LTC3256, thus reducing significant heat and input current.

The LTC3256 is engineered for diagnostic coverage in ISO26262 systems and incorporates numerous safety and system monitoring features. The device is well suited for a variety of applications requiring low noise, low power rails from a high voltage input such as automotive ECU/CAN transceiver supplies, industrial/telecom housekeeping supplies, and general-purpose low-power 12V to 5V and 3.3V conversion.

The efficiency of the LTC3256 is maximised by running the charge pump in 2:1 mode, over as wide an operating range as possible, and automatically switches to 1:1 mode as needed, consistent with VIN and load conditions. Controlled input current and soft switching minimise conducted and radiated EMI.

The device offers low quiescent current of only 20µA with both outputs regulating (no load) and 1µA in shutdown. The integrated watchdog timer, independent power good outputs and reset input ensure reliable system operation and enable fault monitoring. A buffered 1.1V reference output enables system self-testing diagnostics for safety critical applications. Additional safety features include over-current fault protection, over-temperature protection and tolerance of 38V input transients.

The LTC3256 is available in a thermally enhanced 16-lead MSOP package, with a backside thermal pad. The E-grade and I-grade operating junction temperature range is –40°C to 125°, the H-grade operates from –40°C to 150°C, and the MP-grade operates from –55°C to 150°C.

Devices are priced starting at $2.95 each for the E-grade. The USA list pricing shown is for budgetary use only. International prices may differ due to local duties, taxes, fees and exchange rates.

For more information, visit www.linear.com/product/LTC3256

Summary of Features of the LTC3256:

  • Input Voltage Range: 5.5V to 38V
  • Independently Enabled 5V & 3.3V Fixed Outputs
  • 5V Output: 100mA Max
  • 3.3V LDO Output: 250mA Max
  • Multi-Mode Step Down Charge Pump (2:1, 1:1) with Automatic Mode Switching
  • Low Quiescent Current

    • 20µA with Both Outputs Regulating (No Load)
    • ?1µA in Shutdown
  • Engineered for Diagnostic Coverage in ISO26262 Systems
  • 1.1V Reference Output for System Diagnostics
  • Power-On Reset & 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

Applications

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

Linear Technology (UK) Limited

(Now part of Analog Devices)
Tel: +44 (0)1628 477066

E-mail: uksales@linear.com

Web site: www.linear.com

Website for product information:  http://www.linear.com/product/LTC3256