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BQ25170: STAT pin incase of without battery

Shota Mago
Expert 8110 points
Part Number: BQ25170
Other Parts Discussed in Thread: BQ24079T,

Hi team,

My customer considers to use BQ25170 and he is asking about STAT pin behavior.

Datasheet states that STAT pin behaves as below.

1.)  Charge in progress -- Low

2.)   Charge complete -- High 

3.)    Fault -- Blink at 1Hz rate

Meanwhile, STAT pin of Fig 8-3(power-up without battery) blinks around 120ms which is faster than 1Hz.

In addition to above 3 status, STAT pin blinks 120ms frequency when there is no battery. Is this understanding correct?

Also, could you please provide equation to determine RP and RS of TS which can calculate arbitrary threshold?

Best regards,

Shota Mago

 

Regards,

Shota Mago

  • 0
    TI__Guru* 75646 points

    Hello Shota Mago

    Regarding STAT pin BQ25170 and Figure 8-3 behavior.  This is "Power Up Without Battery" and we see the output capacitor charge to 4.2V then have a charge complete condition.  Charger goes to standby with STAT high, but Cout decreases due to slight load.  Voltage reaches recharge point and charge restarts.  The timing in this condition will be determined by Deglitch time to detect charge complete, value of Cout, value of slight load and other.

    RP and RS will adjust TS threshold, what NTC are you using and threshold will you need?

  • 0 in reply to Bill Johns
    TI__Expert 8110 points

    Hi Bill,

    Thanks for your answer.

    Bill Johns said:
    RP and RS will adjust TS threshold, what NTC are you using and threshold will you need?

    When taking recommended 103AT-2 NTC into account, is it possible to set temperature range as 3C to 47C?

    Or setting positive temperature for Vcold side is not possible?

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Guru* 75646 points

    Hello Shoto

    The temp range with only thermistor 103AT-2 NTC used will be 0C to 45C.  Will this be close enough to your target range of 3C to 47C?

  • 0 in reply to Bill Johns
    TI__Expert 8110 points

    Hi Bill,

    I found tool of "Linear Charger NTC Calculator" in BQ24079T product folder page. Its sheet of "Current Source --75uA" looks can be used for BQ25170 if values of I_TS, V_H and V_C are changed properly from the datasheet of BQ25170. 

    According to the tool, RP value becomes negative(error) when value of R_Cold is positive temperature. So TS(cold) of  BQ25170 seems optimized for 0C to negative temperature range. Is this understanding correct?

    Battery's minimum chargeable temp range is 0C. So the customer would like to set Cold side slightly above 0C such as 3C-5C taking tolerance into account.

    Regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Guru* 75646 points

    Hi Shoto

    I have been working with a couple of other calculator tools. Rs and Rp can increase the range, 0C can go lower, 45C can go higher.  But cannot pull 0C higher, as you also found.  

    Is changing the NTC and option?

  • 0 in reply to Bill Johns
    TI__Expert 8110 points

    Hi Bill,

    Thanks for confirmation. It's not sure if they can change NTC. Is there any NTC which can set temp range which the customer requests(3C~43C)?

    Best regards,

    Shota Mago

  • 0 in reply to Shota Mago
    TI__Guru* 75646 points

    Hi Shota

    A couple of things to look at:

    1.) NTC with higher B Value, increases from 3500k to 4000k for 10k.  This will increase the rate resistance increases as temp decreases. Example is the Ametherm ACC024 with B Value of 3892k (B0/50).  Cold shutdown 5C and Hot shutdown 44C. Higher B value will work also along with Rs and Rp.

    2.) BQ25170J has a JEITA temp charging profile with reduced current hot and cold also reduced voltage hot.  Could be an option depending on customer requirements.

  • 0 in reply to Bill Johns
    TI__Expert 8110 points

    Hi Bill,

    Thanks for your suggestion.

    Best regards,

    Shota Mago