SLUS937C December   2009  – December 2019 BQ24072T , BQ24075T , BQ24079T

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Simplified Circuit
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Device Options
  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  Overvoltage Protection (OVP)
      3. 9.3.3  Dynamic Power-Path Management
      4. 9.3.4  Battery Charging
      5. 9.3.5  Charge Current Translator
      6. 9.3.6  Battery Detection and Recharge
      7. 9.3.7  Termination Disable (TD Input, BQ24072T)
      8. 9.3.8  Battery Disconnect (SYSOFF Input)
      9. 9.3.9  Dynamic Charge Timers (TMR Input)
      10. 9.3.10 Status Indicators (PGOOD, CHG)
      11. 9.3.11 Thermal Regulation and Thermal Shutdown
      12. 9.3.12 Battery Pack Temperature Monitoring
    4. 9.4 Device Functional Modes
      1. 9.4.1 Input Source Connected (Adapter or USB)
        1. 9.4.1.1 Input DPM Mode (VIN-DPM)
        2. 9.4.1.2 DPPM Mode
        3. 9.4.1.3 Battery Supplement Mode
      2. 9.4.2 Input Source Not Connected
  10. 10Applications and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 Using the BQ24075T, BQ24079T to Disconnect the Battery from the System
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 Program the Fast Charge Current (ISET):
          2. 10.2.1.2.2 Program the Input Current Limit (ILIM):
          3. 10.2.1.2.3 Program 6.25-hour Fast-Charge Safety Timer (TMR):
          4. 10.2.1.2.4 TS Function:
          5. 10.2.1.2.5 CHG and PGOOD LED Status:
          6. 10.2.1.2.6 Processor Monitoring Status:
          7. 10.2.1.2.7 System ON/OFF (SYSOFF):
          8. 10.2.1.2.8 Selecting IN, OUT and BAT Capacitors
        3. 10.2.1.3 Application Curves
      2. 10.2.2 BQ24072T in a Host Controlled Charger Application
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedures
          1. 10.2.2.2.1 Termination Disable:
        3. 10.2.2.3 Application Curves
  11. 11Power Supply Recommendations
    1. 11.1 Power On
      1. 11.1.1 Half-Wave Adapters
  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 Related Links
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Support Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

9.3.12 Battery Pack Temperature Monitoring

The BQ2407xT features an external battery pack temperature monitoring input. The TS input connects to the NTC thermistor in the battery pack to monitor battery temperature and prevent dangerous over-temperature conditions. During charging, the voltage at TS is continuously monitored. If, at any time, the voltage at TS is outside of the operating range (VCOLD to VHOT), charging is suspended. The timers maintain their values but suspend counting. When the voltage measured at TS returns to within the operation window, charging is resumed and the timers continue counting. When charging is suspended due to a battery pack temperature fault, the CHG output remains low and continues to indicate charging.

Equation 3. BQ24072T BQ24075T BQ24079T eq1_r6a_lus937.gif
Equation 4. BQ24072T BQ24075T BQ24079T eq2_r7a_lus937.gif

Where:

VCOLD = 0.25 X VIN

VHOT = 0.125 X VIN

RHOT is the expected thermistor resistance at the programmed hot threshold, RCOLD is the expected thermistor resistance at the programmed cold threshold. If the value of R6 is less than 100 kΩ, R8 must be added to protect the IC from 28V inputs. If R6 is greater than 100 kΩ, R8 does not need to be used.

BQ24072T BQ24075T BQ24079T ntc_fun_lus937.gifFigure 18. NTC Monitoring Function

For applications that do not require the TS monitoring function, set R6 = 200 kΩ and R7 = 49.9 kΩ to set the TS voltage at a valid level and maintain charging.