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BQ24193: Regarding temperatures in REG09

Southern Engineering
Intellectual 715 points
Part Number: BQ24193
Other Parts Discussed in Thread: BQ25890,

Hi,

The first bits in REG09 hold temperature information. In the datasheet the different bit combinations are described as '000 – Normal,010 – Warm,011 – Cool,101 – Cold,110 – Hot'.

1. Which actual temperatures do these refer to. What is for instance 'Normal' and 'Warm'?

2. Can these bits be used to read the temperature of the IC at any time, or are they only updated if there is an actual fault?

3. If only updated when there is a fault, would there perhaps be a suggested way to trigger an intentional fault to get these temperature bits set?

Thanks!

  • 0
    TI__Guru**** 167116 points

    Hi SE,

    Regarding 1, Cold is 0 C and Hot is 60 C.  Cool and Warm are set by the thermistor and the resistor divider pulled to REGN. 

    Regarding 2, the TS pin is the input to a ladder of comparators that compare V(TS) to fixed thresholds as a % of REGN voltage. See d/s page 8 for percentages.

    Regarding 3, you can overdrive the TS pin using an external voltage source. 

    If you have an ADC or change to BQ25890 with integrated ADC, you use V(TS) to estimate battery temperature as explained in the app note below:

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 715 points

    Hi,

    Regarding 1), is it correct to understand that the complete translation would be this?:

    Cold is <0C, Cool is 0C - 10C, Normal is 10C - 45C, Warm is 45C - 60C and Hot is >60C?

    Regarding 2), I am sorry to say I was a bit unclear. In our setup we have a battery with an NTC connected to the TS pin as recommended. So the BQ24193 will for sure have a good view of the battery (NTC) temperature. At the same time the SW running on our MCU would benefit from knowing this temperature, but unfortunately we do not have an additional ADC available for measuring V(TS) separately. So the SW team was wondering if they could extract this temperature from the BQ24193 over I2C. Hence questions 2 and 3, wondering if the states of REG09[2:0] are continuously updated to show the temperature range the NTC is in, or they are only updated when an actual fault occurs (?). 

    Thanks!

  • 0 in reply to Southern Engineering
    TI__Guru**** 167116 points

    Hi,

    Regarding 1, if your thermistor is the recommended 103AT, then your values for WARM and COOL temp appear to be correct.

    Regarding 2, the charger continuously compares V(TS) to the internal comparators and the bits show the current state: NORMAL, COOL, COLD, WARM or HOT of the TS voltage and therefore battery temperature.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Intellectual 715 points

    Hi,

    Thank you, then it is more clear.

    BTW, should I tell them to read the bits twice every time? That is, is there a risk that the first read of REG09[2:0] represents the NTC temperature at some earlier fault?

    Thanks!

  • 0 in reply to Southern Engineering
    TI__Guru**** 167116 points

    Hi SE,

    The bits change as soon as the voltage on TS trips the comparator voltage (micro-seconds worst case delay).  I don't think that is necessary but wouldn't hurt.

    Jeff

  • 0 in reply to Jeff F
    Intellectual 715 points

    Hi,

    So when reading out REG09[2:0] we do not have to care about the freeze of REG09 mentioned in 8.3.4.3?: 'When a fault occurs, the charger device ... keeps the fault state in REG09 until the host reads the fault register.'

    I was imaging that we for instance would have 'Charge complete' quite often, and was worried that the REG09[2:0] would freeze every time until REG09 was read a second time. That we would fool our selves if using the values from a single read.

    Thanks!

  • 0 in reply to Southern Engineering
    TI__Guru**** 167116 points

    Hi SE,

    Oops. Your are correct.  My bad. I was confusing this part with our newer devices that has TS_STAT bits that report the current status all the time.  This part only has the FAULT bits which need the double read to for the bits to report the current status.

    Regards,

    Jeff