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

11.1 Layout Guidelines

To obtain optimal performance, the decoupling capacitor from IN to GND (thermal pad) and the output filter capacitors from OUT to GND (thermal pad) should be placed as close as possible to the bq21040, with short trace runs to both IN, OUT, and GND (thermal pad).

  • All low-current GND connections should be kept separate from the high-current charge or discharge paths from the battery. Use a single-point ground technique incorporating both the small signal ground path and the power ground path.
  • The high current charge paths into IN terminal and from the OUT terminal must be sized appropriately for the maximum charge current in order to avoid voltage drops in these traces
  • The bq21040 is packaged in a thermally-enhanced MLP package. The package includes a thermal pad to provide an effective thermal contact between the IC and the printed circuit board (PCB); this thermal pad is also the main ground connection for the device. Connect the thermal pad to the PCB ground connection. It is best to use multiple 10mil vias in the power pad of the IC and close enough to conduct the heat to the bottom ground plane. The bottom ground place should avoid traces that “cut off” the thermal path. The thinner the PCB the less temperature rise. The EVM PCB has a thickness of 0.031 inches and uses 2 oz. (2.8mil thick) copper on top and bottom, and is a good example of optimal thermal performance.