Original question:
Hi Dustin,
The bq77915 with the bq7718 seems to work similarly. Notice that from the data sheet parameters the indication is that it will not work, the OW current on the bq7791500 is 100 nA nominal with tolerance while the input current on the bq7718 is +/- 100 nA max. To be certain that this would work based on the parameters a configuration of the bq77915 with higher OW current would be needed.
In practice the bq7718 current is sampled and input current is typically low. OW protection looks much like the figures in the bq7718 data sheet.
At a normal voltage the part will go to UV, then OV before the open wire protection threshold is reached. The bq7718 output goes high when the proper OV level is sustained for its delay time.
The scope probe will pull down the line also of course. Without the probe the signal takes longer to fall:
Note that the OW protection is the lowest system threshold and does not latch. It will be the last protection to set and the first to recover.
At low cell voltage the DSG is already low and an overvoltage will not occur. The OW response time can be seen in the CHG delay from the OW threshold. bq7718 OUT does not go high since there is not an overvoltage condition.
When the cells are at a higher voltage the OV may occur before UV and long before OW.
Drifting of the voltage from varying connection impedance to the cell or pull on the voltage from cell balancing from the OV may make the part change conditions, but these are not related to operation with the bq7718.
