High Voltage Dual Output Step-Down Charge Pump Offers Lower Power Dissipation with No Inductors

Linear Technology LTC3256

Linear Technology Corporation announces the LTC3256, a highly integrated, high voltage low noise dual output power supply, which takes a single positive input and generates 5 V and 3.3 V step-down supplies with high efficiency and no inductors. The device features a wide 5.5 V to 38 V input voltage range and includes independently enabled dual outputs: a 5 V 100 mA supply, and a 250 mA 3.3 V low-dropout (LDO) regulator, for a total of 350 mA available output current. This combination of regulators offers much lower power dissipation than a dual-LDO solution. For example at 12 V VIN and maximum load on both outputs, power dissipation is decreased by over 2 W 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 12 V to 5 V and 3.3 V conversion.

Linear Technology - LTC3256

The LTC3256 maximizes efficiency 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 minimize conducted and radiated EMI. The device offers low quiescent current of only 20 μA with both outputs regulating (no load) and 0.5 μA in shutdown. The integrated watchdog timer, independent power good outputs and reset input ensure reliable system operation and enable fault monitoring. A buffered 1.1 V reference output enables system self-testing diagnostics for safety critical applications. The LTC3256 also has additional safety features including overcurrent fault protection, overtemperature protection and tolerance of 38 V input transients.

LTC3256 -High Efficiency Dual Output Power Supply
High Efficiency Dual Output Power Supply.

The LTC3256 is available in a thermally enhanced 16-lead MSOP package, with a backside thermal pad. The E- and I-grade operating junction temperature range is –40 °C to 125 °C, the H grade operates from –40 °C to 150 °C, and the MP grade operates from –55 °C to 150 °C. Devices are in stock, priced starting at $2.95 each for the E-grade.

Power Dissipation vs Input Voltage
Power Dissipation vs Input Voltage.

Summary of Features: LTC3256

  • Input Voltage Range: 5.5 V to 38 V
  • Independently Enabled 5 V & 3.3 V Fixed Outputs
  • 5 V Output: 100 mA Max
  • 3.3 V LDO Output: 250 mA Max
  • Multi-Mode Step Down Charge Pump (2:1, 1:1) with Automatic Mode Switching
  • Low Quiescent Current
    • 20 μA with Both Outputs Regulating (No Load)
    • ˂0.5 μA in Shutdown
  • Engineered for ISO26262 Diagnostic Coverage in Systems
  • 1.1 V 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

JLCPCP: 2USD 2Layer 5PCBs, 5USD 4Layer 5PCBs

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