SLUUCN4A January 2023 – February 2024
In some user systems, there can be glitches on the supply line during mass production. This can result in a glitch getting to the PACK pin (VPACK), which can then unintentionally wake up a device that was in shutdown.
The feature to manage an unintended wakeup from shutdown, if enabled (with the [CHECK_WAKE] bit), manages a shutdown of the gauge by any allowed shutdown process (except for VOLTAGE BASED SHUTDOWN and POWER SAVE SHUTDOWN, both of which are excluded from this feature). This feature does not function on a wake/start up from a reset.
When this feature is active on wake up from shutdown, the gauge starts a Delay timer (with the default of 2 s) and looks for communication to the gauge during this time—with CHG and DSG FETs remaining off. If during the Delay timer period there is no valid communication with the device, then the device goes back into shutdown (with FETs turned off). If there is valid communication within the Delay timer period, then the device stays in wake and continues like a normal wakeup. Valid communication means the gauge receives a valid address and a command. (It does not matter if the command is invalid. Invalid commands are OK with a valid address.)
One variant to this is the wake up from an IATA shutdown. In this case, each time the gauge wakes up, the IATA function will be called as usual. However, if the gauge then goes back into shutdown (because it was an unintended wakeup from shutdown), then the [IATA_SHUT] bit will be set before going into shutdown again and the FCC and RemCap stored during the original IATA shutdown will still be kept for the next wakeup.
Additionally, the number of times the gauge wakes up from shutdown unintentionally is recorded. This "unintentional wakeup" counter is reset when the gauge wakes up and sees valid communication. If this count exceeds a threshold (Count, with the default of 3), then the next time the gauge wakes up from shutdown, it will execute a normal wakeup without looking for valid communication (and the counter recording wakeup will be reset). If the Count is set to 0, then no threshold exists and the gauge will only wake up with valid communications.
If this feature is enabled ([CHECK_WAKE] set high), then by default the CHG and DSG FETs are off on wake up from SHUTDOWN (during the Delay timer period); thus, the FETs will turn on only if the gauge enters a normal wakeup. However, if the [CHECK_WAKE_FET] bit is set (default is cleared), then the FETs will not be forced off during the Delay timer period.