Auto-Polarity, Millivolt Voltage Step-Up Converter & Power Manager for Thermal Energy Harvesting Applications

Jun 14 2010 - MILPITAS, CA
  • Linear Technology announces the LTC3109, a highly integrated step-up DC/DC converter and power management IC designed to start up and run from millivolt input voltage sources such as thermoelectric generators (TEGs) and thermopiles. The device's groundbreaking and proprietary auto-polarity topology allows it to generate usable power from input voltages as low as ±30mV, enabling temperature differences as low as ±1°C to be harvested in lieu of traditional battery power. This makes it ideal for energy harvesting applications in which the input voltage polarity is unknown or is subject to reversal. Energy harvesters are well suited for applications requiring low average power, even with periodic pulses of higher load current. For example, in many wireless sensor applications the circuitry is only powered to take measurements and transmit data periodically with a low duty cycle.


    The LTC3109 uses two standard compact step-up transformers to provide a complete power management solution. Its 2.2V LDO can power an external microcontroller, and its main output is pin selectable to one of four (2.35V, 3.3V, 4.1V or 5V) fixed voltages to power a sensor, data acquisition circuits and/or a wireless transmitter. A second switched output can be enabled by the host in order to power devices that do not have a micropower shutdown capability. The addition of a storage capacitor provides continuous power even when the input energy source is unavailable or intermittent. The LTC3109's extremely low quiescent current (<7µA) and high efficiency design ensure the fastest possible charge times for the output reservoir capacitor. The combination of the LTC3109's leadless 4mm × 4mm QFN-20 package (or leaded SSOP-20) and very small external components ensure a highly compact solution for energy harvesting applications.

    According to Don Paulus, Vice President and General Manager of Linear's Power Products, “Energy harvesting is an emerging technology with great potential, now poised to break out commercially. The release of the LTC3109, which was developed in cooperation with EnOcean, GmbH, enables a new generation of remote sensor products which can eliminate the need for wired power, batteries or routine maintenance for a wide variety of applications.”

    “Cooperation between EnOcean and Linear Technology means huge advantages for both parties,” says EnOcean's CEO Markus Brehler. “Linear Technology benefits from EnOcean's expertise in energy harvesting for wireless applications, and we, in turn, see benefits in that this new Linear product is especially suitable for powering our energy harvesting wireless modules from small differences in temperature, independent of polarity.”

    The LTC3109EUF is available in a 20-lead 4mm × 4mm QFN package and the LTC3109EGN is available in a SSOP-20 package. Pricing starts at $3.95 each for 1,000-piece quantities. Industrial temperature grade versions, the LTC3109IUF and LTC3109IGN, are also available, priced starting at $4.65 each for 1,000-piece quantities. All versions are available from stock. For more information, visit

    Summary Features LTC3109

    • Operates from Inputs as Low as ±30mV
    • Only ±1°C Needed across TEG to Harvest Energy
    • Proprietary Auto-Polarity Architecture
    • Complete Energy Harvesting Power Management System:
      • Selectable VOUT of 2.35V, 3.3V, 4.1V or 5V
      • 2.2V, 4mA LDO
      • Logic-Controlled Output
      • Energy Storage Capability for Operation during Power Interruption
    • Power Good Indicator
    • Uses Standard Compact Step-up Transformers
    • Small, 20-Pin (4mm × 4mm) QFN or SSOP Packages

    Auto-Polarity, Ultralow Voltage Step-Up Converter & Power Manager


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