BQ27742-G1: the device could not be recovered after faults removed

mike zhang

Part Number: BQ27742-G1
Other Parts Discussed in Thread: BQ27742EVM

Hi there,

I use bq27742EVM to do some protection tests and found out that the device could not be recovered when the faults like OCD or OCC were removed. I have to short the FET between Cell+ and pack+ in order to bring the device back to normal mode. based on the data sheet regarding the operating modes, for OCD fault, the device should exit the OCD fault mode and go back normal mode when the fault mode was removed. but it stayed in the OCD mode until I make the short even there was no fault load. is there something I missed? why did the device behave like that?

Thanks!

Mike

over 6 years ago

0 Onyx Ahiakwo over 6 years ago

TI__Guru* 76230 points

Hi Mike

What is your packp voltage after you have these conditions occured? That is the critical piece for recovery. pls see the TRM,
section 2.2.2.2.1.4 and 2.2.2.2.1.4.1 in the link below:
www.ti.com/.../sluuax0c.pdf

thanks
Onyx

0 mike zhang over 6 years ago in reply to Onyx Ahiakwo

Intellectual 925 points

hi Onyx,

the cell voltage was about 3.9V and pack was about 2.5V when it was in the OCD fault mode and the fault current load also removed (0 or small current set). due to DSG FET OFF, how can the PACKP voltage rise to within 300 mV of the cell voltage?

Thanks!

Mike

0 Onyx Ahiakwo over 6 years ago in reply to mike zhang

TI__Guru* 76230 points

By apply a charger.
thanks
Onyx

0 mike zhang over 6 years ago in reply to Onyx Ahiakwo

Intellectual 925 points

hi Onyx,

for sure by applying a charger on, it will be recovered from the fault mode. but seems like the data sheet doesn't say a charger has to be attached on in order to get out the fault mode. it only says "fault recovery when load removed". is there something I am missing?

thanks!

Mike

0 Onyx Ahiakwo over 6 years ago in reply to mike zhang

TI__Guru* 76230 points

Hi MIKE,
It clearly states the dependence on the packp pin
thanks
Onyx

0 mike zhang over 6 years ago in reply to Onyx Ahiakwo

Intellectual 925 points

hi Onyx,
I got that. but there is no way that the PACKP voltage rises to within 300 mV of the cell voltage without a charger in the case. maybe adding "fault recovery when fault load removed and a charger attached" to the data sheet will end the argument.
Thanks!
Mike

0 Onyx Ahiakwo over 6 years ago in reply to mike zhang

TI__Guru* 76230 points

Hi Mike,
I agree with you. Sorry the document wasn't very explicit.

thanks
Onyx

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BQ27742-G1: the device could not be recovered after faults removed