Integrated power supply needs no inductors

Engineered for diagnostic coverage in ISO26262 systems, the LTC3256 integrated, high voltage low noise dual output power supply, incorporates safety and system monitoring features. Available from Linear Technology, it takes a single positive input and generates 5.0 and 3.3V step-down supplies with high efficiency and no inductors.

There is a wide 5.5 to 38V input voltage range and 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. According to the company, this combination of regulators offers much lower power dissipation than a dual-LDO option. For example at 12V VIN and maximum load on both outputs, power dissipation is decreased by over 2W with the device, reducing heat and input current.

Efficiency 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 20microA with both outputs regulating (no load) and 0.5microA 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 device is suited for applications that require low noise, low power rails from a high voltage input such as automotive ECU/CAN transceiver supplies, industrial/telecomms housekeeping supplies, and general-purpose low-power 12 to 5.0 and 3.3V conversion.

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

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