SLUSB85E May   2013  – January 2016


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  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  Supply Current
    6. 7.6  Digital Input and Output DC Characteristics
    7. 7.7  LDO Regulator, Wake-Up, and Auto-Shutdown DC Characteristics
    8. 7.8  ADC (Temperature and Cell Measurement) Characteristics
    9. 7.9  Integrating ADC (Coulomb Counter) Characteristics
    10. 7.10 Integrated Sense Resistor Characteristics, -40°C to 85°C
    11. 7.11 Integrated Sense Resistor Characteristics, -40°C to 70°C
    12. 7.12 I2C-Compatible Interface Communication Timing Characteristics
    13. 7.13 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
    4. 8.4 Device Functional Modes
    5. 8.5 Programming
      1. 8.5.1 Standard Data Commands
      2. 8.5.2 Control(): 0x00 and 0x01
      3. 8.5.3 Extended Data Commands
      4. 8.5.4 Communications
        1. I2C Interface
        2. I2C Time Out
        3. I2C Command Waiting Time
        4. I2C Clock Stretching
  9. Applications and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. BAT Voltage Sense Input
        2. Integrated LDO Capacitor
        3. Sense Resistor Selection
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendation
    1. 10.1 Power Supply Decoupling
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    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

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • YZF|9
Thermal pad, mechanical data (Package|Pins)
Orderable Information

6 Pin Configuration and Functions

bq27421-G1 Pin_out.gif

Pin Functions

BAT C3 PI, AI LDO regulator input, battery voltage input, and coulomb counter input typically connected to the PACK+ terminal. Connect a capacitor (1 µF) between BAT and VSS. Place the capacitor close to the gauge.
BIN B1 DI Battery insertion detection input. If Operation Configuration bit [BIE] = 1 (default), a logic low on the pin is detected as battery insertion. For a removable pack, the BIN pin can be connected to VSS through a pulldown resistor on the pack, typically the 10-kΩ thermistor; the system board should use a 1.8-MΩ pullup resistor to VDD to ensure the BIN pin is high when a battery is removed. If the battery is embedded in the system, it is recommended to leave [BIE] = 1 and use a 10-kΩ pulldown resistor from BIN to VSS. If [BIE] = 0, then the host must inform the gauge of battery insertion and removal with the BAT_INSERT and BAT_REMOVE subcommands. A 10-kΩ pulldown resistor should be placed between BIN and VSS, even if this pin is unused.
NOTE: The BIN pin must not be shorted directly to VCC or VSS and any pullup resistor on the BIN pin must be connected only to VDD and not an external voltage rail.
GPOUT A1 DO This open-drain output can be configured to indicate BAT_LOW when the Operation Configuration [BATLOWEN] bit is set. By default [BATLOWEN] is cleared and this pin performs an interrupt function (SOC_INT) by pulsing for specific events, such as a change in State of Charge. Signal polarity for these functions is controlled by the [GPIOPOL] configuration bit. This pin should not be left floating, even if unused, so a 10-kΩ pullup resistor is recommended. If the device is in SHUTDOWN mode, then toggling GPOUT will make the gauge exit SHUTDOWN. Therefore, it is recommended to connect GPOUT to a GPIO of the host MCU.
SCL A3 DIO Slave I2C serial bus for communication with system (Master). Open-drain pins. Use with external 10-kΩ pullup resistors (typical) for each pin. If the external pullup resistors will be disconnected from these pins during normal operation, it is recommended to use external 1-MΩ pulldown resistors to VSS at each pin to avoid floating inputs.
SRX C2 AI Integrated high-side sense resistor and coulomb counter input typically connected to system power rail VSYS.
VDD B3 PO 1.8-V Regulator Output. Decouple with 0.47-μF ceramic capacitor to VSS. This pin is not intended to provide power for other devices in the system.
VSS B2, C1 PI Ground pins. The center pin B2 is the actual device ground pin while pin C1 is floating internally and therefore C1 may be used as a bridge to connect to the board ground plane without requiring a via under the device package. It is recommended to route the center pin B2 to the corner pin C1 using a top-layer metal trace on the board. Then route the corner pin C1 to the board ground plane.
(1) IO = Digital input-output, AI = Analog input, P = Power connection