SLUSCE2D April   2016  – January 2019

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 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 Operational Characteristics (Protection Circuits Waveforms)
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Power-Down or Undervoltage Lockout (UVLO)
      2. 8.3.2 Power-up
      3. 8.3.3 Sleep Mode
      4. 8.3.4 New Charge Cycle
      5. 8.3.5 Overvoltage-Protection (OVP) – Continuously Monitored
      6. 8.3.6 CHG Terminal Indication
    4. 8.4 Device Functional Modes
      1. 8.4.1  CHG LED Pull-up Source
      2. 8.4.2  IN-DPM (VIN-DPM or IN-DPM)
      3. 8.4.3  OUT
      4. 8.4.4  ISET
      5. 8.4.5  TS
      6. 8.4.6  Termination and Timer Disable Mode (TTDM) - TS Terminal High
      7. 8.4.7  Timers
      8. 8.4.8  Termination
      9. 8.4.9  Battery Detect Routine
      10. 8.4.10 Refresh Threshold
      11. 8.4.11 Starting a Charge on a Full Battery
  9. 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. 9.2.2.1 Calculations
          1. 9.2.2.1.1 Program the Fast Charge Current, ISET:
          2. 9.2.2.1.2 Pre-Charge and Termination Current Thresholds, ITERM, and PRE-CHG
          3. 9.2.2.1.3 TS Function
          4. 9.2.2.1.4 CHG
        2. 9.2.2.2 Selecting In and Out Terminal Capacitors
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations
      1. 11.3.1 Leakage Current Effects on Battery Capacity
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

8.1 Overview

The bq21040 is a highly integrated single cell Li-Ion and Li-Pol charger. The charger can be used to charge a battery, power a system or both. The charger has three phases of charging: Pre-charge to recover a fully discharged battery, fast-charge constant current to supply the buck charge safely and voltage regulation to safely reach full capacity. The charger is very flexible, allowing programming of the fast-charge current. This charger is designed to work with a USB connection or Adaptor (DC out). The charger also checks to see if a battery is present.

The charger also comes with a full set of safety features: Temperature Sensing Standard, Over-Voltage Protection, DPM-IN, Safety Timers, and ISET short protection. All of these features and more are described in detail below.

The charger is designed for a single power path from the input to the output to charge a single cell Li-Ion or
Li-Pol battery pack. Upon application of a 5VDC power source the ISET and OUT short checks are performed to assure a proper charge cycle.

If the battery voltage is below the LOWV threshold, the battery is considered discharged and a preconditioning cycle begins. The amount of the current goes into the battery during this phase is called pre-charge current. It is fixed to 20% of the fast charge current.

Once the battery voltage has charged to the VLOWV threshold, fast charge is initiated and the fast charge current is applied. The fast charge constant current is programmed using the ISET terminal. The constant current provides the bulk of the charge. Power dissipation in the IC is greatest in fast charge with a lower battery voltage. If the IC reaches 125°C the IC enters thermal regulation, slows the timer clock by half and reduce the charge current as needed to keep the temperature from rising any further. Figure 5 shows the charging profile with thermal regulation. Typically under normal operating conditions, the IC’s junction temperature is less than 125°C and thermal regulation is not entered.

Once the cell has charged to the regulation voltage the voltage loop takes control and holds the battery at the regulation voltage until the current tapers to the termination threshold. The termination current is set to 10% of the fast charge current. The CHG terminal is low (LED on) during the first charge cycle only and turns off once the termination threshold is reached, regardless if termination, for charge current, is enabled or disabled.