BQ20Z655: Unexpected BatteryMode register value

Barrett Bryan

Intellectual 1010 points

Part Number: BQ20Z655

My customer has a battery that is reporting 0x0040 for the BatteryMode() register value.

Per the TI TRM for the gauge. 0x0040 should not occur as the low byte bit 6 is RSVD.

The normally expected values for this battery are 0x0001 (ICC is always = 1)

And 0x0081 (ICC=1 and CF=Condition Cycle Requested).

ICC is even documented by TI as always fixed to 1, but with 0x0040 it isn’t, so it’s a little concerning on what the gauge firmware is doing…

Is there some sort of explanation for this anomaly?

over 6 years ago

0 Batt over 6 years ago

TI__Mastermind 42535 points

Barrett,

I'll have to talk to the fw guys and figure out why ICC is turning to 0. It shouldn't. Do you by any chance have a log for this run?
Bits that are set to RSVD are usually there because they are not used, or are used for internal debugging. I'll talk to the fw engineers and reply here.

0 Batt over 6 years ago in reply to Batt

TI__Mastermind 42535 points

Quoting the fw engineer, "One possibility is if their system wrote to battery mode register as this is writable in all modes, otherwise firmware does not do nothing, even bit is set, it’s harmless, no action is taken.". The RSVD bit also does nothing.

0 Barrett Bryan over 6 years ago in reply to Batt

TI__Intellectual 1010 points

Can you check to make sure we're talking about the same RSVD bit? The datasheet states that the low byte should be read-only.

0 Batt over 6 years ago in reply to Barrett Bryan

TI__Mastermind 42535 points

Yeah, that's the bit I was referring to given that the register value you mentioned was 0x0040.

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BQ20Z655: Unexpected BatteryMode register value