LTC1760 without safety signals

In one of the new projects we are  looking at the battery charger IC LTC1760 from analog devices.
In this,  I have question regarding custom battery interface .
In case battery connected to the LTC1760 doesn't provide temperature  sensor voltage as seen in other SMBUS compliant battery connector ( BAT+, BAT-, TEMP,SCL,SDA). 
*Can the LTC1760 still function by using internal temperature information over SMBUS ?
* Will LTC1760 try to get temperature  over SMBUS inspite of having safety signal pins for temperature measurement?
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  • 0
    •  Analog Employees 
    on Aug 10, 2020 5:21 PM 5 months ago

    Hello,

    I am not sure what you mean by "provide temperature sensor voltage".

    The LTC1760 biases the thermistor pin for its own temperature measurements. It does not report these measurements to the user, but uses them to qualify charging in accordance with the smart battery specification.

    The LTC1760 will not get temperature information over SMBus. It just reads the thermistor signal pin. The battery handles its own temperature compensation, so the LTC1760's function is for redundancy only.

    Regards,

    Zack

  • Thanks for the reply.

    Does that mean we can still use LTC1760 with  NC to pins  TH1A,TH1B,TH2A,TH2B . LTC1760 can still charge batteries and operate as per specification.

  • 0
    •  Analog Employees 
    on Aug 11, 2020 6:43 PM 5 months ago in reply to PAVAN_ZOE

    No, you need those connections. A safety signal (the thermistor in this case) is a requirement for smart battery charging and the LTC1760 will not let you charge without it.

    In this case, LTC1760 also uses the thermistor connection to detect battery presence, so that is another reason you need to use the thermistor connections.

    Many batteries don't actually have a real thermistor on their thermistor pin. It is often just a 300 ohm resistor. This puts the charger into a "normal charging with a timeout on wake-up charging" mode. Still, the connection is necessary to allow charging at all.

    Regards,
    Zack

  • We have our own custom batteries with non standard connector interface. This interface doesn't provide  thermister pins. Can I use voltage divider and connect constant voltage to the PIns  TH1A,TH1B,TH2A,TH2B  and use LTC1760 .

    .

  • +1
    •  Analog Employees 
    on Aug 12, 2020 5:05 PM 5 months ago in reply to PAVAN_ZOE

    You can't apply a constant voltage, but you can use a "dummy" thermistor. You still need the normal TH1A, TH1B, TH2A, & TH2B resistors in place. Just put a resistor where the thermistor would normally go. 300ohms is typical.

    Note that this will impact operation. Since the LTC1760 uses thermistor to detect battery presence, that means it will think both batteries are installed at all times. It will try to wake-up charge them, for example. You can work with this, but it is something to be aware of.

    If your batteries have any sort of safety signal, you could use that to switch these resistors in/out upon connection of the batteries. You don't need an actual thermistor, just something to have the batteries say "honey, I'm home".

    Regards,

    Zack

Reply
  • +1
    •  Analog Employees 
    on Aug 12, 2020 5:05 PM 5 months ago in reply to PAVAN_ZOE

    You can't apply a constant voltage, but you can use a "dummy" thermistor. You still need the normal TH1A, TH1B, TH2A, & TH2B resistors in place. Just put a resistor where the thermistor would normally go. 300ohms is typical.

    Note that this will impact operation. Since the LTC1760 uses thermistor to detect battery presence, that means it will think both batteries are installed at all times. It will try to wake-up charge them, for example. You can work with this, but it is something to be aware of.

    If your batteries have any sort of safety signal, you could use that to switch these resistors in/out upon connection of the batteries. You don't need an actual thermistor, just something to have the batteries say "honey, I'm home".

    Regards,

    Zack

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