BQ27Z746: upper limit delay time in sleep mode

Customer also need the way to calculate max  actual delay time about hardware protection,hope your concern ,thank you~

Hello,

This question this question has been assigned and will be reviewed when possible.

Thank you,
Alan

The gauge should not be in sleep mode if the current is 1A. I assume that you configured the gauge to exit sleep mode for a current that high. See the table in 7.3.1 for exit from sleep conditions. A current that high will typically trigger the wake comparator so this will wake up the gauge immediately and it will start measuring current and run its algorithm once a second. The delay times are relative to the gauge's 1 second cycle timing so the protection delay may be up to 1 second later than expected (if the threshold was exceeded right after the previous measurement was taken).

Thanks for your analysis,yes the max delay time from sleep,not always keeping in sleep mode. i'm still confused about why it will exit sleep immediately cause the table 7.3.1 describes "The device wakes up every Voltage Time to measure voltage and temperature.The device continues to coulomb count and update current

every 4 s." If it means current or voltage won't be measured immediately?
And more,how to understand the returning to normal but wait until 4s current measurement.The test data indicates that the delay time exceeds the set value by more than 2 seconds,even to 4s.

There's a wake comparator that will pull it out of sleep faster than the measurement interval. It doesn't take 4 seconds for the gauge to update current.

FW protection runs on a 1 second cycle so once the gauge is out of sleep and measures current (after 1 second) then the gauge will run the protection code and it will apply all rules for each firmware controlled protection event.

Thanks for your reply.Though the waveform shows a different condition.
May I ask if you are referring to the Hardware i-wake?This indeed helps understand the delayed discharge current protection, but are there other immediate wake-up parameter settings for charging current protection /voltage protection and temperature protection? Thank you

The gauge needs to wake up for FW protections to work because those require active measurements every second.

There aren't any other settings to wake the gauge up. Note that the HW protections (supercomp) still work, regardless of sleep or normal mode.

In this product, the HW protection thresholds are more lenient than FW protection thresholds with shorter protection delay time.

Is this configuration reasonable? In this scenario, will it lead to longer FW wake-up time and delay protection duration?

The idea is for the protector to protect against severe conditions (extreme currents, extreme voltages) immediately (because it has the hardware comparator to do so which doesn't need firmware running) and less severe conditions whenever the firmware runs its conversion and protection code (1 second cycle in normal mode).

That's why HW protection thresholds are usually higher (and also much more granular) than FW protection thresholds.