SLUSBJ3D August 2013  – February 2015


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1Absolute Maximum Ratings
    2. 6.2ESD Ratings
    3. 6.3Recommended Operating Conditions
    4. 6.4Thermal Information
    5. 6.5Electrical Characteristics
    6. 6.6Typical Characteristics
  7. Detailed Description
    1. 7.1Overview
    2. 7.2Functional Block Diagram
    3. 7.3Feature Description
      1. 7.3.1Maximum Power Point Tracking
      2. 7.3.2Battery Undervoltage Protection
      3. 7.3.3Battery Overvoltage Protection
      4. 7.3.4Battery Voltage in Operating Range (VBAT_OK Output)
      5. 7.3.5Push-Pull Multiplexer Drivers
      6. 7.3.6Nano-Power Management and Efficiency
    4. 7.4Device Functional Modes
      1. 7.4.1Main Boost Charger Disabled (Ship Mode) - (VSTOR > VSTOR_CHGEN and EN = HIGH)
      2. 7.4.2Cold-Start Operation (VSTOR < VSTOR_CHGEN, VIN_DC > VIN(CS) and PIN > PIN(CS))
      3. 7.4.3Main Boost Charger Enabled (VSTOR > VSTOR_CHGEN, VIN_DC > VIN(DC) and EN = LOW )
      4. 7.4.4Thermal Shutdown
  8. Application and Implementation
    1. 8.1Application Information
      1. 8.1.1Energy Harvester Selection
      2. 8.1.2Storage Element Selection
      3. 8.1.3Inductor Selection
      4. 8.1.4Capacitor Selection
        1. Capacitance
        2. Capacitance
        3. Capacitance
        4. Capacitance on VSTOR or VBAT_SEC
    2. 8.2Typical Applications
      1. 8.2.1Solar Application Circuit
        1. Requirements
        2. Design Procedure
        3. Performance Plots
      2. 8.2.2TEG Application Circuit
        1. Requirements
        2. Design Procedure
        3. Performance Plots
      3. 8.2.3Piezoelectric Application Circuit
        1. Requirements
        2. Design Procedure
        3. Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1Layout Guidelines
    2. 10.2Layout Example
    3. 10.3Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1Device Support
      1. 11.1.1Third-Party Products Disclaimer
      2. 11.1.2Zip Files
    2. 11.2Documentation Support
      1. 11.2.1Related Documentation
    3. 11.3Trademarks
    4. 11.4Electrostatic Discharge Caution
    5. 11.5Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Orderable Information

1 Features

  • Ultra Low-Power With High-Efficiency DC-DC Boost Charger
    • Cold-Start Voltage: VIN ≥ 330 mV
    • Continuous Energy Harvesting From Input Sources as Low as 100 mV
    • Ultra-Low Quiescent Current of 325 nA
    • Input Voltage Regulation Prevents Collapsing High-Impedance Input Sources
    • Ship Mode With < 5 nA From Battery
  • Energy Storage
    • Energy can be Stored to Rechargeable Li-Ion Batteries, Thin-Film Batteries, Super-Capacitors, or Conventional Capacitors
  • Battery Charging and Protection
    • Internally Set Undervoltage Level
    • User-Programmable Overvoltage Level
  • 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 Maximum Power Point Tracking (MPPT)
    • Integrated MPPT for Optimal Energy Extraction From a Variety of Energy Harvesters
  • Gate Drivers for Primary (Nonrechargeable) and Secondary (Rechargeable) Storage Element Multiplexing
    • Autonomous Switching Based on VBAT_OK
    • Break-Before-Make Prevents System Rail Droop

2 Applications

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

3 Description

The bq25505 device is specifically designed to efficiently extract the microwatts (µW) to miliwatts (mW) of power generated from a variety of DC energy harvesting, high-impedance sources like photovoltaic (solar) or thermal electric generators (TEGs) without collapsing those sources. The battery-management features of the bq25505 ensure that a secondary rechargeable battery is not overcharged by this extracted power, with voltage boosted, nor depleted beyond safe limits by a system load. The integrated multiplexer gate drivers autonomously switch the system load to a primary nonrechargeable battery if the secondary battery voltage falls below the user-defined VBAT_OK threshold.

Device Information(1)

bq25505VQFN (20)3.50 mm x 3.50 mm
  1. For all available packages, see the orderable addendum at the end of the datasheet.

Simplified Schematic

bq25505 solar_cir_lusbj3.gif

Charger Efficiency

bq25505 C002_SLUSBH2.png