Hi,
We have a custom board on which we are using the BQ78350 with the BQ76940 to monitor and protect 15 cells. To avoid causing damage, we simulate the cells by connecting an external power supply across the battery and we have resistances that can be connected or disconnected depending on whether the cells are present or not.
We were trying to trigger the AOLD protection to make sure that it was working. We cleared the RSNS bit to 0 and we cleared the threshold (OCD_D0-OCD_D3) bits to 0 to the lowest current to trigger the protection as low as possible. It should be at 8mV across the sense. We have also raised the OCD threshold above the AOLD to make sure that it doesn't interfere with the tests that we are doing.
From my understanding, the AOLD protection works by measuring the voltage across the sense resistor and the protection will be triggered if the threshold is passed.
We have a 2mOhm resistance so according the TRM, a 4A current should be sufficient to cause an 8mV difference across the sense.
We went as high as 6.5A and we measured the voltage at the BQ76940 sense pins and I had 13mV which should have triggered the AOLD protection.
The protection is enabled (Enabled Protection A). The Enabled removal protections are disabled.
I know the protections are working because I can get the CUV and COV protections to work with the external power supply.
Why is the AOLD protection not working? Are we missing something?
We will be testing the ASCD protection the same way but I would like to know that the AOLD works before testing something that could possibly damage our board.
Thanks for your help