High-voltage dual-output step-down charge pump offers lower power dissipation without inductors



LTC3256 Step-Down Charge Pump with Watchdog Timer and Reference Output

Linear Technology announced the LTC3256, 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 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 20μA with both outputs regulating (no load) and 0.5μA 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. The LTC3256 also has additional 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 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. For more information, visit www.linear.com/product/LTC3256.

Summary of Features: 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)
<0.5μA in Shutdown
Engineered for ISO26262 Diagnostic Coverage in 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

Pricing shown is for budgetary use only and may differ due to local duties, taxes, fees and exchange rates.

Linear Technology