SLUSDV2A May   2020  ā€“ May 2021 BQ25798


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Description (continued)
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Device Power-On-Reset
      2. 8.3.2  PROG Pin Configuration
      3. 8.3.3  Device Power Up from Battery without Input Source
      4. 8.3.4  Device Power Up from Input Source
        1. Power Up REGN LDO
        2. Poor Source Qualification
        3. ILIM_HIZ Pin
        4. Default VINDPM Setting
        5. Input Source Type Detection
          1. D+/Dā€“ Detection Sets Input Current Limit
          2. HVDCP Detection Procedure
          3. Connector Fault Detection
      5. 8.3.5  Dual-Input Power Mux
        1. ACDRV Turn On Condition
        2. VBUS Input Only
        3. One ACFET-RBFET
        4. Two ACFETs-RBFETs
      6. 8.3.6  Buck-Boost Converter Operation
        1. Force Input Current Limit Detection
        2. Input Current Optimizer (ICO)
        3. Maximum Power Point Tracking for Small PV Panel
        4. Pulse Frequency Modulation (PFM)
        5. Device HIZ State
      7. 8.3.7  USB On-The-Go (OTG)
        1. OTG Mode to Power External Devices
        2. Backup Power Supply Mode
        3. Backup Mode with Dual Input Mux
      8. 8.3.8  Power Path Management
        1. Narrow VDC Architecture
        2. Dynamic Power Management
      9. 8.3.9  Battery Charging Management
        1. Autonomous Charging Cycle
        2. Battery Charging Profile
        3. Charging Termination
        4. Charging Safety Timer
        5. Thermistor Qualification
          1. JEITA Guideline Compliance in Charge Mode
          2. Cold/Hot Temperature Window in OTG Mode
      10. 8.3.10 Integrated 16-Bit ADC for Monitoring
      11. 8.3.11 Status Outputs ( STAT, and INT)
        1. Charging Status Indicator (STAT Pin)
        2. Interrupt to Host ( INT)
      12. 8.3.12 Ship FET Control
        1. Shutdown Mode
        2. Ship Mode
        3. System Power Reset
      13. 8.3.13 Protections
        1. Voltage and Current Monitoring
          1.  VAC Over-voltage Protection (VAC_OVP)
          2.  VBUS Over-voltage Protection (VBUS_OVP)
          3.  VBUS Under-voltage Protection (POORSRC)
          4.  System Over-voltage Protection (VSYS_OVP)
          5.  System Short Protection (VSYS_SHORT)
          6.  Battery Over-voltage Protection (VBAT_OVP)
          7.  Battery Over-current Protection (IBAT_OCP)
          8.  Input Over-current Protection (IBUS_OCP)
          9.  OTG Over-voltage Protection (OTG_OVP)
          10. OTG Under-voltage Protection (OTG_UVP)
        2. Thermal Regulation and Thermal Shutdown
      14. 8.3.14 Serial Interface
        1. Data Validity
        2. START and STOP Conditions
        3. Byte Format
        4. Acknowledge (ACK) and Not Acknowledge (NACK)
        5. Slave Address and Data Direction Bit
        6. Single Write and Read
        7. Multi-Write and Multi-Read
    4. 8.4 Device Functional Modes
      1. 8.4.1 Host Mode and Default Mode
      2. 8.4.2 Register Bit Reset
    5. 8.5 Register Map
      1. 8.5.1 I2C Registers
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. PV Panel Selection
        2. Inductor Selection
        3. Input (VBUS / PMID) Capacitor
        4. Output (VSYS) Capacitor
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

Charging Safety Timer

The device has a built-in safety timer to prevent an extended charging cycle due to abnormal battery conditions. The user can program the fast charge safety timer through I2C (CHG_TMR bits). When the fast charge safety timer expires, the fault register CHG_TMR_STAT bit is set to 1, and an INT pulse is asserted to the host. The trickle charge timer is fixed 1 hour. The pre-charge safety timer is adjustable 2 hours (POR default) or 0.5 hour. The fast charging timer POR default setting is 12 hours.

The trickle charge, pre-charge and fast charge safety timers can be disabled by setting EN_TRICHG_TMR, EN_PRECHG_TMR or EN_CHG_TMR bit to 0. Each charging safety timer can be enabled anytime regardless of the current charging state. Each timer restarts counting when it is enabled. As soon as each charging stage is initiated, the associated safety timer starts to count, which is illustrated in the battery charging profile chart shown in Section

During input voltage, current or thermal regulation, the safety timer counts at half-clock rate as the actual charge current is likely to be below the register setting. For example, if the charger is in input current regulation (IINDPM_STAT = 1) throughout the whole charging cycle, and the safety timer is set to 5 hours, then the timer will expire in 10 hours. This half-clock rate feature can be disabled by setting TMR2X_EN = 0. If the host disables the half-clock rate while the charger is already running at half-clock rate, the charger keeps running at the half-clock rate and the half-clock rate is not disabled until the charger exit the voltage, current or thermal regulation.

During faults which disable charging or supplement mode, the timer is suspended. Since the timer is not counting in this state, the TMR2X_EN bit has no effect. Once the fault goes away, the safety timer resumes. The pre-charge safety timer and the trickle charge safety timer follow the same rules as the fast charge safety timer in terms of getting suspended, reset and counting at half-rate when TMR2X_EN is set.

The fast charge timer is reset at the following events:

  1. Charging cycle stop and restart (toggle CE pin, EN_CHG bit, or charged battery falls below recharge threshold after termination)
  2. BAT voltage changes from pre-charge to fast-charge or vice versa (in host-mode or default mode)
  3. A change of the value of CHG_TMR[1:0] register bits

The pre-charge timer is reset at the following events:

  1. Charging cycle stop and restart (toggleCE pin, EN_CHG bit, or charged battery falls below recharge threshold)
  2. BAT voltage changes from trickle charge to pre-charge or vice versa, pre-charge to fast charge or vice versa (in host-mode or default mode)
  3. A change of the value of PRECHG_TMR register bit.

The trickle charge timer is reset at the following events:

  1. Charging cycle stop and restart (toggleCE pin, EN_CHG bit, or charged battery falls below recharge threshold)
  2. BAT voltage changes from trickle charge to pre-charge or vice versa (in host-mode or default mode)