SLUSBH2G March   2013  – March 2019

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application Schematic
      2.      Charger Efficiency vs Input Voltage
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Electrical Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Maximum Power Point Tracking
      2. 7.3.2 Battery Undervoltage Protection
      3. 7.3.3 Battery Overvoltage Protection
      4. 7.3.4 Battery Voltage within Operating Range (VBAT_OK Output)
      5. 7.3.5 Storage Element / Battery Management
      6. 7.3.6 Programming OUT Regulation Voltage
      7. 7.3.7 Step Down (Buck) Converter
      8. 7.3.8 Nano-Power Management and Efficiency
    4. 7.4 Device Functional Modes
      1. 7.4.1 Main Boost Charger Disabled (Ship Mode) - (VSTOR > VSTOR_CHGEN and EN = HIGH)
      2. 7.4.2 Cold-Start Operation (VSTOR < VSTOR_CHGEN, VIN_DC > VIN(CS) and PIN > PIN(CS), EN = don't care)
      3. 7.4.3 Main Boost Charger Enabled (VSTOR > VSTOR_CHGEN and EN = LOW )
        1. 7.4.3.1 Buck Converter Enabled (VSTOR > VBAT_UV, EN = LOW and VOUT_EN = HIGH )
      4. 7.4.4 Thermal Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Energy Harvester Selection
      2. 8.1.2 Storage Element Selection
      3. 8.1.3 Inductor Selection
        1. 8.1.3.1 Boost Charger Inductor Selection
        2. 8.1.3.2 Buck Converter Inductor Selection
      4. 8.1.4 Capacitor Selection
        1. 8.1.4.1 VREF_SAMP Capacitance
        2. 8.1.4.2 VIN_DC Capacitance
        3. 8.1.4.3 VSTOR Capacitance
        4. 8.1.4.4 VOUT Capacitance
        5. 8.1.4.5 Additional Capacitance on VSTOR or VBAT
    2. 8.2 Typical Applications
      1. 8.2.1 Solar Application Circuit
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
      2. 8.2.2 TEG Application Circuit
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
      3. 8.2.3 Piezoelectric Application Circuit
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
        3. 8.2.3.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.1.2 Detailed Design Procedure

The recommended L1 = 22 µH with ISAT ≥ I-CHG(CBC_LIM)MAX, L2 = 10 µH with ISAT ≥ I-BUCK(CBC_LIM)MAX, CBYP = 0.01 µF and low leakage CREF = 10 nF are selected. In order to ensure the fastest recovery of the harvester output voltage to the MPPT level following power extraction, the minimum recommended CIN = 4.7 µF is selected. Because no large system load transients are expected and to ensure fast charge time during cold start, the minimum recommended CSTOR = 4.7 µF.

No MPPT resistors are required because VOC_SAMP can be tied to VSTOR to give 80% MPPT.

  • Keeing in mind VBAT_UV < VBAT_OV ≤ 5.5 V, to size the VBAT_OV resistors, first choose RSUMOV = ROV1 + ROV2 = 13 MΩ then solve Equation 2 for
    • Equation 12. bq25570 Eq11_Rov1_slusbj3.gif
  • ROV2 = RSUMOV - ROV1 = 13 MΩ - 5.62 MΩ = 7.38 MΩ → 7.32 MΩ resulting in VBAT_OV = 4.18V due to rounding to the nearest 1% resistor.
  • Keeping in mind VBAT_OV ≥ VBAT_OK_HYST > VBAT_OK ≥ VBAT_UV, to size the VBAT_OK and VBAT_OK_HYST resistors, first choose RSUMOK = ROK1 + ROK2 + ROK3 = 13 MΩ then solve Equation 3 and Equation 4 for
    • Equation 13. bq25570 Eq12_ROK1_slusbj3.gif
    Equation 14. bq25570 Eq13_ROK2_slusbj3.gif
  • ROK3 = RSUMOK - ROK1 - ROK2 = 13 MΩ - 5.62 MΩ - 5.479 MΩ = 1.904 MΩ → 1.87 MΩ to give VBAT_OK = 2.39 V and VBAT_OK_HYST = 2.80 V.
  • For VOUT, first choose ROUT1 + ROUT2 = RSUMOUT = 13 MΩ, then solve Equation 5 for ROUT1 = VBIAS / VOUT x RSUMOUT = 1.21 V / 1.8 V x 13 MΩ = 8.74 MΩ → 8.66 MΩ after rounding to nearest 1% value.
  • ROUT2 = RSUM - ROUT1 = 13 MΩ - 8.66 MΩ = 4.34 MΩ → 4.22 MΩ after rounding.

SLUC484 provides help on sizing and selecting the resistors.