Hi!
We have a question regarding permanent fails during safety undervoltage.
We have a setup that looks like this:
SUV_THRESHOLD 0x92CB : 0x0708 (1800mv)
PROTECTION_CONFIGURATION 0x925F : 0x0732 ( PF_OTP and PF_FUSE is enabled)
( Say that we have SHUTDOWN_CELL_VOLTAGE 0x923F : 0x3E8 (1000mV) )
At the SUV level, the voltage is not high enough to be able to enable the fuse drive (with our fuse). Hence, we aimed to rely on OTP programing of the permanent fail to permanently disable the pack. Our problem is that as it seems, the permanent failed flag is not set if we recharge the cells back over the SUV limit. We have not performed any partial reset when starting up from shutdown this time...
In the documentation of the BQ76942 (11.3 Secondary Protections), we read "OTP programming may be delayed in low-voltage and high-temperature conditions until OTP programming can reliably be accomplished.". What does this mean?
With the given SUV threshold, can the OTP programing be performed? We have a feeling that even if so - it might take longer time than is available to us at these low voltage levels.
Best regards
//Erik Almqvist