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

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 V_IN 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).