SLUS724F September   2006  – January 2022 BQ2022A

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics: DC
    6. 6.6 Switching Characteristics: AC
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 1024-Bit EPROM
      2. 7.3.2 EPROM Status Memory
      3. 7.3.3 Error Checking
      4. 7.3.4 Customizing the BQ2022A
      5. 7.3.5 Bus Termination
    4. 7.4 Device Functional Modes
    5. 7.5 Programming
      1. 7.5.1  Serial Communication
      2. 7.5.2  Initialization
      3. 7.5.3  ROM Commands
        1. 7.5.3.1 READ ROM Command
        2. 7.5.3.2 SKIP ROM Command
      4. 7.5.4  Memory/Status Function Commands
      5. 7.5.5  READ MEMORY Commands
        1. 7.5.5.1 READ MEMORY/Page CRC
        2. 7.5.5.2 READ MEMORY/Field CRC
      6. 7.5.6  WRITE MEMORY Command
      7. 7.5.7  READ STATUS Command
      8. 7.5.8  WRITE STATUS Command
      9. 7.5.9  PROGRAM PROFILE Byte
      10. 7.5.10 SDQ Signaling
      11. 7.5.11 RESET and PRESENCE PULSE
      12. 7.5.12 WRITE Bit
      13. 7.5.13 READ Bit
      14. 7.5.14 PROGRAM PULSE
      15. 7.5.15 IDLE
      16. 7.5.16 CRC Generation
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Programming Circuit Example
        2. 8.2.2.2 SDQ Master Best Practices
      3. 8.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
      2. 11.2.2 Receiving Notification of Documentation Updates
    3. 11.3 Trademarks
    4. 11.4 Support Resources
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

9 Power Supply Recommendations

The BQ2022A is a low-power device that only needs to be turned on when communicating. The device power comes from the voltage supply that is used for digital I/O in the system. A dedicated VCC pin does not exist in the device for which there is not a requirement of a supply input bypass capacitor. The device obtains its power from the SDQ communication input which can be sustained during normal communication activity.

The ramp time of the SDQ voltage when power is initially applied may be slow due to current limiting from the source. Ramp times greater than 200 µs might cause undesired bouncing of the POR circuit and result in the device not generating a presence pulse. To account for this undesired effect on the device a best practice for the communication master would be to issue a “hard” reset to the device by pulling down the SDQ line for >5 ms and then releasing the SDQ bus before issuing the reset pulse that is approximately 480 µs long.

GUID-1EC9445F-D438-426F-A178-76DE1F38000B-low.gif Figure 9-1 Power Up Best Practice

Figure 9-1 illustrates the best practice for dealing with initial power on ramps, shown as (1) in the figure, that may be long in duration. The host should issue a “hard” reset, (2), of > 5 ms, which resets the device and generate a presence delay and presence pulse, (3). After that, a “soft” reset of approximately 480 µs can be applied, (4), which also generates a high presence delay and low presence pulse, (5).