SLAAEV0 July   2026 BQ79616-Q1

 

  1.   1
  2.   Abstract
  3. 1Basic Principle of Reverse Wake-up for BQ79616
    1. 1.1 Basic Principle of Reverse Wake-up Implemented by BQ79616 and BQ79600
    2. 1.2 OVUVOTUT Function of BQ79616
    3. 1.3 Logic for BQ79600 to Implement Reverse Wake-up
  4. 2How to Configure BQ79616 and BQ79600 to Achieve Reverse Wake-up Function
    1. 2.1 Configuration for BQ79616 to Implement Reverse Wake-up Function
    2. 2.2 Configuration for BQ79600 to Implement Reverse Wake-up Function
    3. 2.3 Other Configurations for BQ79600 and BQ79616 Prior to Entering Sleep
  5. 3Testing of Reverse Wake-up Based on EVM Board
    1. 3.1 Reverse Wake-up Test with BQ79600 Operating in Sleep Mode
    2. 3.2 Reverse Wake-up Test with BQ79600 Operating in Shutdown Mode
  6. 4Summary
  7. 5References

1.1 Basic Principle of Reverse Wake-up Implemented by BQ79616 and BQ79600

Block Diagram of BQ79600/BQ79616 Reverse Wake-up FunctionFigure 1-1 Block Diagram of BQ79600/BQ79616 Reverse Wake-up Function

The figure above shows the reverse wake-up system block diagram of a conventional BMS, wherein multiple BQ79616 chips are used as AFEs to accomplish the monitoring of all cell voltages and temperatures of the battery pack. The BQ79600 is used as a bridge chip connecting the AFEs and the MCU to perform the conversion and transmission of communication data. The function where the BMS operates in low-power mode to monitor the battery pack for OVUVOTUT and Heartbeat signals and reverse-wakes the BMS after a battery pack fault occurs is referred to as the reverse wake-up function of the AFE. Usually, the reverse wake-up function requires a loop daisy chain.

To realize the reverse wake-up function, the BQ79600 can operate in Sleep mode or Shutdown mode with the Sniff function enabled. The power consumption of the BQ79600 operating in Sleep mode is slightly higher than that in Shutdown mode; Shutdown mode saves power consumption but loses the diagnostic capability for the two communication lines—forward and reverse—between the BQ79600 and the first AFE, as well as the last AFE.

Unlike the BQ79600, the BQ79616 must operate in Sleep mode. Before the BQ79616 enters Sleep mode, the alarm thresholds for OVUVOTUT must be properly configured. After entering Sleep mode, the TSREF of the BQ79616 remains constantly powered, executing real-time fault diagnostics for OVUVOTUT. Concurrently, if the diagnostic function for the Heartbeat tone signal is enabled, the BQ79616 can also diagnose the Heartbeat signal to judge the integrity of the AFE ahead of it as well as the intermediate communication lines. In a fault-free state, the BQ79616 periodically transmits a Heartbeat tone every 400ms. Once an OVUVOTUT fault occurs or the Heartbeat is lost for over 1s, the BQ79616 will immediately cease transmitting the Heartbeat tone and switch to transmitting a Fault tone instead. After receiving the Fault tone, the BQ79616 behind it will also immediately begin transmitting the Fault tone, ultimately relaying the Fault tone to the BQ79600.

Upon receiving the Fault tone at its communication port, the BQ79600 pulls the INH level high. The INH level acts as a hardware wake-up signal for the SBC/PMIC after being stepped down by a voltage divider resistor network to wake up the SBC/PMIC. Then, the MCU is woken up by the SBC/PMIC. After being woken up, the MCU first wakes up the BQ79600, and then transmits a Sleep2active tone via the BQ79600 to wake up the BQ79616. Once woken up, the BMS performs fault diagnostics. After obtaining the specific fault, it executes the corresponding measures according to the severity of the fault level hazard.