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Texas Instruments BQ25570

Ultra Low Power Harvester Power Management IC with Boost Charger, and Nanopower Buck Converter

Overview

TopologyBoost Converter
Input voltage-0.3-5.5 V
Output 12 V
IC revisionE

Description

The bq25570 is a highly integrated energy harvesting Nano-Power management solution that is well suited for meeting the special needs of ultra low power applications. The product is specifically designed to efficiently acquire and manage the microwatts (µW) to milliwatts (mW) of power generated from a variety of DC sources like photovoltaic (solar) or thermal electric generators. The bq25570 is the first device of its kind to implement a highly efficient boost charger with a nano-powered buck converter targeted toward products and systems, such as wireless sensor networks (WSN) which have stringent power and operational demands. The design of the bq25570 starts with a dc/dc boost converter/charger that requires only microwatts of power to begin operating. Once started, the boost charger can effectively extract power from low voltage output harvesters such as thermoelectric generators (TEGs) or single or dual cell solar panels. The boost charger can be started with VIN as low as 330 mV, and once started, can continue to harvest energy down to VIN = 100 mV.

The bq25570 also implements a programmable maximum power point tracking sampling network to optimize the transfer of power into the device. The fraction of open circuit voltage that is sampled and held can be controlled by pulling VOC_SAMP high or low (80% or 50% respectively) or by using external resistors. This sampled voltage is maintained via internal sampling circuitry and held with an external capacitor (CREF) on the VREF_SAMP pin. For example, solar cells typically operate with a maximum power point (MPP) of 80% of their open circuit voltage. Connecting VOC_SAMP to VSTOR sets the MPPT threshold to 80% and results in the IC regulating the voltage on the solar cell to ensure that the VIN_DC voltage does not fail below the voltage on CREF which equals 80% of the solar panel's open circuit voltage. Alternatively, an external reference voltage can be provided by a MCU to produce a more complex MPPT algorithm. In addition to the boost charging front end, the bq25570 provides the system with an externally programmable regulated supply via the buck converter. The regulated output has been optimized to provide high efficiency across low output currents (< 10 µA) to high currents (~110 mA).

The bq25570 is designed with the flexibility to support a variety of energy storage elements. The availability of the sources from which harvesters extract their energy can often be sporadic or time-varying. Systems will typically need some type of energy storage element, such as a re-chargeable battery, super capacitor, or conventional capacitor. The storage element will make certain constant power is available when needed for the systems. The storage element also allows the system to handle any peak currents that can not directly come from the input source.

To prevent damage to a customer’s storage element, both maximum and minimum voltages are monitored against the internally set under-voltage (UV) and user programmable over-voltage (OV) levels.

To further assist users in the strict management of their energy budgets, the bq25570 toggles the battery good (VBAT_OK) flag to signal an attached microprocessor when the voltage on an energy storage battery or capacitor has dropped below a pre-set critical level. This should trigger the reduction of load currents to prevent the system from entering an under voltage condition. There is also independent enable signals to allow the system to control when to run the regulated output or even put the whole IC into an ultra-low quiescent current sleep state.

All the capabilities of bq25570 are packed into a small foot-print 20-lead 3.5mm × 3.5 mm QFN package (RGR).

Features

  • Ultra Low Power DC/DC Boost Charger
  • Cold-start Voltage: VIN ≥ 330 mV
  • Continuous Energy Harvesting From VIN as low as 100 mV
  • Input Voltage Regulation Prevents Collapsing High Impedance Input Sources
  • Full Operating Quiescent Current of 488 nA (typical) Ship Mode with < 5 nA From Battery
  • Energy Storage
  • Energy can be Stored to Re chargeable Li-ion Batteries,Thin-film Batteries, Super-capacitors, or ConventionalCapacitors
  • Battery Charging and Protection
  • Internally Set Undervoltage Level
  • User Programmable Overvoltage Levels
  • Battery Good Output Flag
  • Programmable Threshold and Hysteresis
  • Warn Attached Microcontrollers of Pending Loss of Power
  • Can be Used to Enable or Disable System Loads
  • Programmable Step Down Regulated Output (Buck)
  • High Efficiency up to 93%
  • Supports Peak Output Current up to 110 mA (typical)
  • Programmable Maximum Power Point Tracking (MPPT)
  • Provides Optimal Energy Extraction From a Variety of Energy Harvesters including Solar Panels, Thermal and Piezo ElectricGenerators

Typical applications

  • Wireless Sensor Networks (WSN)
  • Portable and Wearable Health Devices
  • Environmental Monitoring
  • Thermal Electric Generator (TEG) Harvesting
  • Entertainment System Remote Controls
  • Bridge and Structural Health Monitoring (SHM)
  • Low Power Wireless Monitoring
  • Solar Charger
  • Energy Harvesting
  • Smart Building Controls

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