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BQ79612-Q1: Fluctuation in AUX REFL leading to SM133 failure in BQ79612 ASIC chips. (At Scania CV)

Part Number: BQ79612-Q1

Problem :

We were having problem with SM133(Aux REFL diagnosis).

According to data sheet VACC_AUX_REFL needs to be within 1.092V and 1.106V.

Our set up consists of 20 BQ circuits connected in the daisy chain with real battery packs. 

During the test with the BQ79612 chips we observe the reference voltage VACC_AUX_REFL from the random BQ circuits in the chain violating the threshold with up to 40mV fluctuations.

We see a maximum of 1.118V and a minimum of  1.069V measured from the ADC.

This behaviour is now consistent, that if we run the pack for some time, we always seem to get this issue on the BQ79612 chips.



1.    Is the threshold for VACC_AUX_REFL 1.092V to 1.106V ?  Or what are the acceptable range of values for VACC_AUX_REFL without violating the safety ?                                                                                                    2.    What does this threshold violation mean, is it a damaged ASIC?                                                                                                                                                                                                                                                    3.    How does the violation of SM133 affect the ASIC with respect to safety?                                                                                                                                                                                                                                  4.    Is there a way to make external measurements on the ASIC circuitry?