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OT2D flag when TS2 is not being used

George Mortimer
Expert 1205 points
Other Parts Discussed in Thread: BQ20Z655-R1

Gentlemen;

I am in the process of manufacturing a new battery pack using the bq20z655-R1 chip.  I am currently having a problem with the discharge FET not turning on because of an OT2D flag in the Safety Status 2 block.  The problem is that I am not using TS2 in this design.  Currently I have the TS2 input grounded (the same procedure I have used previously with the bq20z90V150 chip), and the Operation Cfg A register, low byte, bits 4 and 3, set to 01 (TS1 input). Is there a difference in the way the 20z655 responds to unused thermistor inputs?

Also, in the initial setup of the #1 board, I am finding a severe error in the voltage calibration. with a (simulated) cell stack voltage of 14.0V applied, the pack is reading 15.88V. I attempted to run a voltage calibration from the PRO screen and got a 5024 voltage gain calibration overflow error.  Any guesses as to what might be going on here?

  • 0
    Expert 1205 points

    Gentlemen;

    I managed to find the solution on my own.  I was unaware that in migrating from the 20z90 to the 20z655 there is a separate setup for TS1 and TS2, and if TS2 is not used one needs to set them to zero (unused).  I was operating under the impression that setting the OpCfgA bits to only use TS1 would completely shut down any action from TS2 - apparently it does not, and each TS has to be set (or disabled) independently.

    Also, regarding the calibration error, it is apparently due to noise on the VCELL+ line which I inadvertently failed to tie to a filter capacitor.