SLUAAF8 October   2021 BQ24707 , BQ24707A , BQ24725A , BQ24735 , BQ24770 , BQ24780S , BQ24800 , BQ25700A , BQ25708 , BQ25710 , BQ25720 , BQ25730 , BQ28Z610-R1 , BQ4050 , BQ40Z50 , BQ40Z50-R1 , BQ40Z50-R2 , BQ40Z80

 

  1.   Trademarks
  2. 1Introduction
  3. 2Smart Battery Setup
    1. 2.1 Gauge Setup
      1. 2.1.1 I2C System Differences
    2. 2.2 Charger Setup
  4. 3Communication Protocol
  5. 4Data Collected
  6. 5Summary
  7.   A Appendix
    1.     A.1 General Setup
    2.     A.2 Gauge Setup - SMBus
    3.     A.3 Gauge Setup - I2C
    4.     A.4 Charger Setup
    5.     A.5 Charge Voltage Example
    6.     A.6 Charge Current Example
  8.   B References

3 Communication Protocol

Using the register bit definitions outlined in the data sheet of the charger, the charge current and voltage writes can be verified using a logic analyzer or oscilloscope. For the BQ40Z50 and other SMBus devices, the communications in broadcast mode can be PEC enabled with the SBS configuration[CPE] bit. SBS configuration[HPE] does not affect this system because there is no host. If both SBS configuration[HPE] and SBS configuration[CPE] are disabled the gauge will not transmit a PEC byte during any communication. The current and voltage are transmitted from the gauge in little endian, so the format of transmission is the following when the SBS configuration[CPE] bit is set:

Charger address (write) -> Register to write -> Least significant byte -> Most significant byte -> PEC Byte.

For the I2C-based system the package structure is the same, except the Packet Error Checking (PEC) byte is not used for I2C-based systems so there are no PEC enable options for the BQ28Z610-R1.