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BQ51050B: Using BQ51050 with Wired Charging

Daniel McLane87
Prodigy 50 points
Part Number: BQ51050B
Other Parts Discussed in Thread: BQ24040, , BQ51013B

We are integrating wireless charging into a device that may also charge from a 5V USB charger. 

The BQ51050B datasheet (figure 37) shows how to add a BQ24040 to support wired charging.  I do not understand the function of the TS/CTL pin in this diagram.  

Questions:

1) The diagram shows the NTC resistor connected to the BQ24040. Does this mean that the BQ51050B does not monitor battery temperature during charging?  How does it safely charge if not?

2) The BQ51050B datasheet states "The TS/CTRL pin offers three functions: • NTC temperature monitoring • Charge done indication • Fault indication".  So question is, how does the Charge Done and Fault indication work?  Is this pin an output in this case?  Unclear on how to use this pin correctly. 

Thanks for your help.

  • 0
    TI__Guru* 75806 points
    Hello
    Circuit is figure 37 only shows one connection to the NTC with bq24040 a 2ed NTC would have to be added for the bq51050B.
    The TS/CTRL pin is can be pulled low to set fault, pulled high to set charge complete or high Z for normal NTC temp monitoring.
    See bq51013B data sheet section 8.3.14 for better explanation and circuit example.

    Also the 013B could be used to power the bq24040 in a similar circuit see figure 48.
  • 0 in reply to Bill Johns
    Prodigy 50 points

    Bill -

    Thanks for your timely response. The discussion in the BQ51013B is clear.  I suggest that this be edited into the BQ51050B datasheet.

    Dan

  • 0 in reply to Bill Johns
    Prodigy 70 points

    Hello Bill,

    You wrote "..one connection to the NTC with bq24040 a 2ed NTC would have to be added for the bq51050B." Do I really need a second NTC unit or can I just connect the NTC to both IC's? 

    Can you give me a NTC example for easy plug and play or maybe an NTC which is used for TI's eval boards? 

    Best regards!

    Pascal 

  • 0 in reply to user_0815
    TI__Guru* 75806 points
    Hello
    The two cannot be connected together each device will need its own NTC.
    Value of the NTC will depend on the range you are looking for.
  • 0 in reply to Bill Johns
    Prodigy 70 points

    Hello,

    can you please explain why I need two separate NTC's?

    Best regards

  • 0 in reply to user_0815
    Prodigy 70 points
    And could you please update your NTC calculation tool "sluc629" to support Excel 2016?! I always get an "missing bibliothek" error.

    Thanks a lot!
  • 0 in reply to user_0815
    TI__Guru* 75806 points

    Hello

    What temp range are you looking for on the design, 0C to 50C?

    "Can you please explain why I need two separate NTC's?"

    If the bq24040 and bq5105X are configured in parallel to charge the same battery then each one will need it's own NTC to monitor temp. 

    The bq24040 will use a current source to develop a voltage on the NTC that is monitor by comparators.

    The bq5105X will use a voltage source to develop a voltage on the NTC that is also measured by comparators, But this voltage source is only on during comm time, about every 250mS.  

    The two TS pins will accomplish the same function but differently.

  • 0 in reply to Bill Johns
    TI__Guru* 75806 points
    "And could you please update your NTC calculation tool "sluc629" to support Excel 2016?! I always get an "missing bibliothek" error."

    Thanks for the feed back, will see what I can do.
  • 0 in reply to Bill Johns
    Prodigy 70 points
    Gotcha! Thanks for your explanation. I didn't mention the two different measurement methods.

    "What temp range are you looking for on the design, 0C to 50C?" Yes these specification fit for our application. Do you have some example NTC circuits for me?

    Best regards!