SLUAAT5 December   2023 BQ25756

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2LiFePO4 Charging Profile
  6. 3BQ25756 Settings For LiFePO4
    1. 3.1 Set Charging Voltages
      1. 3.1.1 Regulation Voltage
      2. 3.1.2 Recharge Voltage
      3. 3.1.3 Battery Low Voltage
    2. 3.2 Set Charging Current
      1. 3.2.1 Charging Current
        1. 3.2.1.1 ICHG Pin Pull Down Resistor
        2. 3.2.1.2 ICHG_REG Register Bits
      2. 3.2.2 Pre-Charge Current
      3. 3.2.3 Termination Current
    3. 3.3 TS Pin Setting
      1. 3.3.1 JEITA Enabled
      2. 3.3.2 JEITA Disabled
      3. 3.3.3 NTC Monitoring Disabled
  7. 4Supercapacitor Charging Profile
  8. 5SBQ25756 Settings For Supercapacitor
    1. 5.1 Charge Current Setting
    2. 5.2 Charge Voltage Setting
    3. 5.3 TS Pin Setting
  9. 6Test Results From EVM
    1. 6.1 Charging LiFePO4 Battery
    2. 6.2 Charging Supercapacitor
  10. 7Summary
  11. 8References

6.2 Charging Supercapacitor

For charging supercapacitor on the EVM, EN_PRECHG, EN_TERM and EN_CHG_TMR is disabled using bqStudio. VFB_REG is set to 1.562 V to achieve charge voltage of 14.5 V. Charging current is set to 2 A. Input voltage is at 31 V. A 1.67 F discharged capacitor is attached for charging. When EN_CHG is enabled, the charger charges the capacitor with full fast charge current. When the capacitor reaches 14.5 V, charge current is tapered down. The charge status register is shown as ‘taper charge’. At this stage STAT1 pin is ON and STAT2 pin is OFF. Because the termination has been turned off, the charger status stays at the taper charge phase indefinitely to keep the supercapacitor charged at 14.5 V.

GUID-20231205-SS0I-FD92-JZRB-V5P70C2V78QB-low.svg Figure 6-2 Supercapacitor Charging Cycle on the EVM