SLUSCM2B October   2017  – November 2018

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Typical Application Circuit
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
    1.     Pin Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Undervoltage Lockout (UVLO)
      2. 9.3.2 Power On
      3. 9.3.3 Overvoltage Protection (OVP)
      4. 9.3.4 Dynamic Power-path Management
        1. 9.3.4.1 Input Source Connected (Adapter or USB)
          1. 9.3.4.1.1 Input DPM Mode (VIN-DPM)
          2. 9.3.4.1.2 DPPM Mode
          3. 9.3.4.1.3 Battery Supplement Mode
        2. 9.3.4.2 Input Source Not Connected
      5. 9.3.5 Battery Charging
        1. 9.3.5.1 Charge Current Translator
        2. 9.3.5.2 Battery Detection And Recharge
        3. 9.3.5.3 Battery Disconnect (SYSOFF Input)
        4. 9.3.5.4 Dynamic Charge Timers (TMR Input)
        5. 9.3.5.5 Status Indicators (PGOOD, CHG)
        6. 9.3.5.6 Thermal Regulation And Thermal Shutdown
      6. 9.3.6 Battery Pack Temperature Monitoring
      7. 9.3.7 Half-Wave Adaptors
    4. 9.4 Device Functional Modes
      1. 9.4.1 Sleep Mode
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application – bq24079QW-Q1 Charger Design Example
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Calculations
          1. 10.2.2.1.1 Program the Fast Charge Current (ISET):
          2. 10.2.2.1.2 Program the Input Current Limit (ILIM)
          3. 10.2.2.1.3 Program 6.25-hour Fast-Charge Safety Timer (TMR)
        2. 10.2.2.2 TS Function
        3. 10.2.2.3 CHG and PGOOD
        4. 10.2.2.4 System ON/OFF (SYSOFF)
        5. 10.2.2.5 Selecting In, Out And Bat Pin Capacitors
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Thermal Package
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Third-Party Products Disclaimer
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • RGT|16
Thermal pad, mechanical data (Package|Pins)
Orderable Information

9.3.5.4 Dynamic Charge Timers (TMR Input)

The bq24079QW-Q1 device contains internal safety timers for the pre-charge and fast-charge phases to prevent potential damage to the battery and the system. The timers begin at the start of the respective charge cycles. The timer values are programmed by connecting a resistor from TMR to VSS. The resistor value is calculated using the following equation:

Equation 4. tPRECHG = KTMR × RTMR
Equation 5. tMAXCHG = 10 × KTMR × RTMR

Leave TMR unconnected to select the internal default timers. Disable the timers by connecting TMR to VSS.

Note that timers are suspended when the device is in thermal shutdown, and the timers are slowed proportionally to the charge current when the device enters thermal regulation.

During the fast charge phase, several events increase the timer durations.

  1. The system load current activates the DPPM loop which reduces the available charging current
  2. The input current is reduced because the input voltage has fallen to VIN(LOW)
  3. The device has entered thermal regulation because the IC junction temperature has exceeded TJ(REG)

During each of these events, the internal timers are slowed down proportionately to the reduction in charging current. For example, if the charging current is reduced by half, the timer clock is reduced to half the frequency, and the counter counts half as fast.

If the pre charge timer expires before the battery voltage reaches VLOWV, the bq24079QW-Q1 indicates a fault condition. Additionally, if the battery current does not fall to ITERM before the fast charge timer expires, a fault is indicated. The CHG output flashes at approximately 2 Hz to indicate a fault condition. The fault condition is cleared by toggling CE or the input power, entering/ exiting USB suspend mode, or an OVP event.